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Schattenbach
2018-09-25, 11:41 AM
Hello everyone,

since over one year ago, whenever i felt like it, I’ve worked on creating a new D20 System that’s intending to use some of the most useful bits of the OGL content of Pathfinder 1e, DnD3.5/D20Modern/D20Future, Classless BESM D20, the D20 Mecha and a few other OGL D20 systems combined with the general workings of BESM 3e/TriStats/dX Attributes and such and to use them to form a solid baseline for high powered settings such some western fantasy/western animation/comic book settings or settings such as Little Garden (Mondaiji tachi ga Isekai Kara Kuru Sō Desu yo? Light Novel Setting), Gensokyo (Touhou Main Setting), the Nasuverse (Type Moon Settings), the ToAru-Verse (i.e. ToAru Majutsu no Index and Toaru Kagaku no Railgun and such) as well as diverse Xianxia (i.e. high-powered chinese cultivation worlds) settings, all of which host beings with highly diverse power levels ranging from ordinary humans to well beyond the scale of planet destroying or star crushing gods and demons. And even if someone isn’t looking any of that, the various subsystems that make up the rules framework should still prove useful when wanting to use a great variety of games.

Neither of the systems I mentioned above are particularly perfect (for example, Tri-Stat dX and BESM 3e have some issues with Attribute pricing/cost scaling ... and this is far worse in BESM D20) while D20 generally breaks down it its mechanics at higher levels when it comes to the combat and skill system (doesn’t even need wonky Spells/Spell rules and, much worse, Epic Spell rules for that), so taking some of the best options out of all these systems as well as some additional rulings seems like the best solution to that.

If someone is wondering about why I’m doing that ... its because there currently aren’t really all that much systems out there that are capable to actually emulate the settings mentioned above and because and there’s just so much good stuff in the BESM/TriStat and D20 OGL System that it’s hard to give up on using that.

I’m planning to make the entire system be OGL/OGL-like so that anyone that wants to enjoy it or that wants to create supplements or subsystems and such for it can do so without issue.

The primary purpose of this thread is for me to inform about stuff that’s finished, to gather feedback and insights, to discuss some D20 mechanics and what issues might crop up. When I’m looking for some people to playtest some stuff, I’m going to make a separate thread for that if necessary.

So if someone is interested in this, please feel free to post.

For those interested, here are is some (although incomplete) information regarding the current state of progress:

#Aptitude System (finished, is compatible with all RPG systems)

#General Adjustment of the Attribute System (partially finished)
##Adjustments and Guidelines for problematic Attributes (partially finished)
##Adjustments and Guidelines for problematic Disabilities (partially finished)
##Designing Existence, Creature and other fundamental Attributes (partially finished)
##Discussing how to handle Energy differently in various settings (partially finished
##Special Attributes for Transcendent Beings (partially finished)

#Fixing the Spellcasting System (partially finished)
##Fixing the issues with insufficient DC-scaling for spells/etc. at higher levels. (partially finished, indirectly helped by fixing escalating bonus-types)
##Fixing insufficient HP damage scaling at higher levels (partially finished, indirectly helped by fixing escalating HP progression)
##Fixing general mechanical issues (partially finished)
##Modifications for rules regarding Spell-like abilities and Spells from items ... (finished)
##Getting ride of wands (at least in their regular DnD3.5/Pathfinder form) ... (finished)
##Creating Spell Slot System for mastered spells (basically finished)

#Making sure Monsters/NPCs and PCs play by the same rules

#General Adjustment of the Skill System (nearly finished)
##Option 1: Transforming Skills into Attributes and adjusting their general capabilities (nearly finished)
##Option 2: Keeping a modified Skill System with different Skill Point cost for each Skill (nearly finished)
##Re-purposing the function of INT (basically finished)

#Ensuring that basic capabilities/things everyone should be (at least with some baseline training) able to do AREN’T Class-locked/Level-locked/Feat-chain-locked etc. (basically finished)

#Handling ECL/HD/RHD (basically finished)

#Fixing HP scaling issues at high levels (basically finished)

#Fixing Bonus Scaling issues at higher levels (partially finished)

#General Adjustment of the Feat System (partially finished)
##Option 1: Getting ride of several feats
##Option 2: Overhaul of feats and capabilities in general.
##Option 3: Getting ride of skills entirely (unfinished)

#Quasi-Realistic Combat System (partially finished)
##Fluid and comprehensive Action Economy (basically finished)
##Taking Excellent performance/vast difference in skill into account
##Injury and Death (basically finished)
##Adjustments and Guidelines for Combat Modifiers (partially finished)
#Introducing Armour (and Structural Armour) into the combat System (finished)
##Collateral damage (partially finished)
##Damage to Weapons and Equipment during combat (partially finished)

#Devastation System for Object and Mass destruction (basically finished)
##Modern Vehicle and Weapon Reference Chart (Optional, partially finished)

Schattenbach
2018-09-25, 01:12 PM
Placeholder Post for future use.

Schattenbach
2018-09-25, 01:59 PM
Placeholder Post for future use.

Schattenbach
2018-09-25, 05:17 PM
Placeholder Post for future use.

noob
2018-09-26, 08:12 AM
##Fixing insufficient HP damage scaling at higher levels (partially finished, indirectly helped by fixing escalating HP progression)

In fact in dnd 3.5 it is quite the opposite problem: at high level people deals too much damage for the hitpoints of the target because then they start doing stuff like full round attacking with power attack and dealing half of the hit points of the opponent in one round(more when using luminous weapons or other weapons like that) in core and the more manuals are added the worse it is.
So it ends up being around level 5 that you are the more survivable and above you progressively become frailer and frailer relatively to an attack routine.
Unless you plan to make it different from the other d20 systems and remove iterative and weapons with growing efficiency(for example in D20 modern people gets killed rather quickly by excessive damage and the increasing amount of firepower people packs).

Schattenbach
2018-09-26, 02:50 PM
Thanks for the feedback.


In fact in dnd 3.5 it is quite the opposite problem: at high level people deals too much damage for the hitpoints of the target because then they start doing stuff like full round attacking with power attack and dealing half of the hit points of the opponent in one round(more when using luminous weapons or other weapons like that) in core and the more manuals are added the worse it is.
So it ends up being around level 5 that you are the more survivable and above you progressively become frailer and frailer relatively to an attack routine.
Unless you plan to make it different from the other d20 systems and remove iterative and weapons with growing efficiency(for example in D20 modern people gets killed rather quickly by excessive damage and the increasing amount of firepower people packs).

Just like you said ... Physical attacks in DnD3.5 do quite well (though one of the main reasons for that is DnD3.5 power attack, which has design problems on its own):
for two-handed weapon attacks and such which typical ranges from the basic [four attacks per round with (2d6 + 1.5x(STR Modifier) + 1/4x(BAB)x3 + some other bonus-types to damage)] to the difficult to hit ([four attacks per round with (2d6 + 1.5x(STR Modifier) + 1x(BAB)x3 + some other bonus-types to damage)], more attacks if dual wielding.

The problem here is that [(number of HD)*(HD + CON Modifier)] arguably scales much faster than, for example, things like:
for spells/special abilities/military weapons/natural hazards/etc. ... [1d6 damage per Caster Level/HD] /[1d8 damage per Caster Level/HD]/[2d6 damage per Caster Level/HD]/[1d10 damage per Caster Level/HD] and such or whatever scaling military weapons/natural hazards in DnD3.5/D20 modern/D20 future seem to use.

This doesn’t get any better at higher levels once enough CON-boosting stuff is at hand or creatures acquire quite a lot of CON by other means.

Then there’s the issue with evasion being a single dip away and Save DCs generally scaling much slower than Paladin dip/Blackguard dip and/or Resistance/Insight/Luck/Sacred/Profane/whatever bonuses from items and other sources and full permanent immunity to a lot of stuff (including all five elemental damage types) is a cheap investment at higher levels. Damage-type Spells are typically capped, too (requiring a +4 metamagic to bring them up to standard, though it’s possible to reduce that cost with taking that one epic feat I don’t remember several times), though at least the use of Empower+Maximize that +7 Intensified Spell(doubles and maximizes) manages to produce acceptable numbers until CON-modifier goes even higher (i.e. significantly beyond +15 or so)

The way HP scales in relation to damage is a fundamental mechanical fault and adding even more crazy ways to multiply damage numbers (or Ubercharging/lots of extra damage per hit/Epic Spellcasting) at higher levels just to keep things working fine is at best a band aid, not a way to resolve fundamental mechanical problems. And it seems to be simpler to fix the way HP and Power attack and other things such as that scale (Pathfinder’s Power attack, for example, is much more manageable in that regard) than to fix how everything else could possibly scale.

About the combat system ... I’m using an Action Economy that draws most of its aspects from BESM D20 and Pathfinder’s Unchained Action Economy (i.e. 3 Actions per round, additional attacks each with cumulative -5 penalty, etc.) with some additional rules added in. So no iterative attacks but there are ways to attack multiple times per turn and (at least theoretically) ways to get more actions per turn (i.e. through Attributes that grant extra actions).

Regarding multiple attacks: To begin with, BESM 3e/Tri-Stat dX/BESM D20 use the Armour Attribute (which in its basic form - that has problems on its own - is basically uber-damage reduction), which reduces the effect of multiple weaker attacks compared to one bigger and more powerful attack significantly, anyway (though lots of attacks with extra damage bonuses and attempts to crit-fish would still manage to bypass this to some unintended degree if that was all what is there to keep numbers in check).

I hope I didn’t miss anything in there. Do you have some additional questions or suggestions or want to point out something else that I might’ve missed?

Schattenbach
2018-09-30, 07:13 AM
As it turns out, I still didn’t get down to actually sort out and formulate some of the stuff out I wanted to formulate ...

I would like some opinion regarding the math behind HP in relation to Damage and other defensive measures ... the math seems to work out fine but that doesn’t mean I didn’t miss something.

Here are some combat rules and such.

]HP/Energy Calculation formulas:
(Health Points based on HP per HD) + 5x((positive Constitution Modifier) + (positive Charisma Modifier)) + HDx(Negative Constitution Modifier) + (Bonus health points)

Energy Point Calculation Formular: (Energy Points per HD) + 5x((positive Charisma Modifier) + (positive Wisdom Modifier)) + HDx(Negative Charisma Modifier) + (Bonus Energy Points)

Important Note: Typical humanoid adults (humans, etc.) are assumed to possess at least 2HD due being grown up.

Regular ways to get Health points and Energy points:

Charisma score ... costs at higher levels (over 25 Charisma) is 1CP per standard Ability Score increase (so 2CP for actual Modifier increases) ... provides 5 Energy points per point of Charisma modifier and also provides 5 Heath points per point of Charisma modifier ... provides various other benefits; as such – and because high Charisma further protect against the lethal threat of excessive Ability damage and drain – one could assume that each increase of 5 Energy points only costs 0.75CP and each increase of 5 Healt points only costs 0.75CP at higher levels.

Constitution score ... costs at higher levels (over 25 Constitution) is 1CP per standard Ability Score increase (so 2CP for actual Modifier increases) ... provides 5 Health points per point of Constitution modifier - i.e. 5 Health Points per invested CP - ... provides its bonus to Fortitude Saves and various other benefits; as such – and because high Constitution further protect against the lethal threat of excessive Ability damage and drain – one could assume that each increase of 5 Healt points only costs 0.75CP at higher levels.

Wisdom score ... costs at higher levels (over 25 Constitution) is 1CP per standard Ability Score increase (so 2CP for actual Modifier increases) ... provides 5 Energy points per point of Constitution modifier ... provides its bonus to Will Saves and various other benefits; as such – and because high Wisdom further protect against the lethal threat of excessive Ability damage and drain – one could assume that each increase of 5 Healt points only costs around 0.75CP at higher levels.

"Energy Bonus" Attribute ... 1CP per Rank ... provides 8 Energy Points per Rank, i.e. 8 Energy Points per invested CP
"Energy Dice" (part of HD) ... 1CP per Rank ... provides 1d8 Energy Points per CP, i.e. at most 8 Energy Points per invested CP, unimproved average of 4.5 Energy points per CP

Note: Some fundamental Attributes further boost the Energy Points provided by the "Energy Dice" and the "Energy Bonus" Attribute. Training can improve Average Energy points up to
the maximum and some other advanced Attributes automatically maximize the Energy points per HD. With the targeted number basic numbers higher levels being 1d10 Health points, i.e. up to 10 Energy Points per CP and avg. 5.5 Energy Points per CP, through the “Energy Dice” and 10 Energy Points per CP through the “Energy Bonus” attribute.

"Health Bonus" Attribute ... 1CP per Rank ... provides 8 Health points per Rank, i.e. 8 Energy Points per invested CP
"HP Dice" (part of HD) ... 1CP per Rank ... provides 1d8 Energy Points per CP, i.e. at most 8 Energy Points per invested CP, unimproved average of 4.5 Health points per CP

Note: Some fundamental Attributes further boost the Health points provided by the "HP Dice" and the "Health Bonus" Attribute. Training can improve Average Health points up to the maximum and
some other advanced Attributes automatically maximize the HP per HD. With the targeted number basic numbers higher levels being 1d10 Health points, i.e. up to 10 Health Points per CP and avg. 5.5 Health Points per CP, through the “Health Dice”
and 10 Health Points per CP through the “Health Bonus” attribute.

Additional Details regarding Hit Dice:
1d4 HP cost 0.5CP ... i.e. in and itself at most 8 HP per CP invested, unimproved average of 4.5 HP per CP
1d6 HP cost 0.75CP ... i.e. in and itself at most 8 HP per CP invested, unimproved average of 4.5 HP per CP
1d8 HP cost 1CP ... i.e. in and itself at most 8 HP per CP invested, unimproved average of 4.5 HP per CP
1d10 HP cost 1.25CP ... i.e. in and itself at most 8 HP per CP invested, unimproved average of 4.5 HP per CP
1d12 HP cost 1.5CP ... i.e. in and itself at most 8 HP per CP invested, unimproved average of 4.5 HP per CP

1d4 Energy Points cost 0.5CP ... i.e. in and itself at most 8 Energy Points per CP invested, unimproved average of 4.5 Energy points per CP
1d6 Energy Points cost 0.75CP ... i.e. in and itself at most 8 Energy Points per CP invested, unimproved average of 4.5 Energy points per CP
1d8 Energy Points cost 1CP ... i.e. in and itself at most 8 Energy Points per CP invested, unimproved average of 4.5 Energy points per CP
1d10 Energy Points cost 1.25CP ... i.e. in and itself at most 8 Energy Points per CP invested, unimproved average of 4.5 Energy points per CP
1d12 Energy Points cost 1.5CP ... i.e. in and itself at most 8 Energy Points per CP invested, unimproved average of 4.5 Energy points per CP

Discussing basic Sources of Damage that can practically be used without resource usage besides attack actions and character points:
various weapon-types …
Strength modifier: basic damage of up to 1 or 1.5 … cost at higher levels 1CP per increase, i.e. 0.5 or 0.75 points of damage per CP, with some options to obtain Strength modifiers possibly being unchanged at 0.5CP/Rank, i.e. 1 or 1.5 points of damage per CP.
BAB & Power Attack (and Deatly Aim): basic damage of up to 2 or 3 per point of reduced BAB, BAB costs 3CP/Rank, i.e. 0.67 or 1 point of damage per CP. Somewhat unbalanced compared to other damage options, so it might be better to simply get ride of power attack as it might just be a bit too good of a feature.
Massive Damage Attribute (specific Attack form): 2 points of precision damage to each attack of specificied attack form per Rank at 1CP/Rank, i.e. 2 point of precision damage per CP.
Massive Damage Attribute (all Attack form): 2 points of precision damage to each attack of all attack form per Rank at 2.5CP/Rank, i.e. 0.8 points of precision damage per CP.
Sneak Attack: priced at ~2CP each for 1d6 precision damage that applies to multiple forms of attacks, i.e. avg. of 1.75 precision damage per CP.
Critical hits do increase these numbers accordingly.

#ARMOUR ATTRIBUTE CP PRICING

4 points of Armour per Rank (with lower pricing obviously resulting in more Armour relative to CP investment).

Armour Attribute Pricing for Natural Armour and Damage Reduction:
4CP/Rank … Structural Armour (blocks basically all forms of HP damage)
3CP/Rank … Integrated Armour (blocks damage of all physical damage types),
3CP/Rank ... Natural Armour (blocks damage of all physical damage types),
2.5CP/Rank ... Damage Reduction without any bypass requirements
2CP/Rank ... Damage Reduction with up to five combined bypass requirements that are creature-compatible (i.e. the bypass requirements of have to make sense for the creature in question based on its overall characteristics)
1.5CP/Rank ... Damage Reduction with up to three combined bypass requirements (i.e. up to two additional “and” requirements) that are creature-compatible (i.e. the bypass requirements of have to make sense for the creature in question based on its overall characteristics)
1CP/Rank ... Damage Reduction with one bypass requirement (i.e. no combined bypass requirement) that is creature-compatible (i.e. the bypass requirements of have to make sense for the creature in question based on its overall characteristics)

Note: The five typical requirement categories for bypassing DR are damage-type, good/evil, chaotic/lawful, material-type and magic/epic.



Other combat gimmicks ...


##############################################
#CHARACTER ACTIONS

The Action System integrates several parts of the Pathfinder “Unchained” Action System into the Action System of BESM D20 Combat System, while further supplementing it with some other rules from basic D20, D20 Mecha as well as other sources.

#Each round, each creature has three Actions it can take during its turn as well a 1 Reaction to perform out of turn actions. Each Action typically requires 1 Action, with some Actions potentially requiring 2 or more actions.
#Each Attack Action after the first attack Action is performed with cumulative -5 penalty to the Attack roll.
#Defense rolls, as per the standard BESM D20 rules, do never – just like reflex saves – use up actions, though each additional roll after the first one is performed with cumulative penalty of -2. Whenever Creatures would perform Defense Rolls at a penalty because of this, they can opt to use one Reaction to perform the Defense Roll at no penalty.

Note: Strength Modifier and Dexterity Modifier do no longer, as per the Standard BESM D20 rules, provide to-Hit bonuses on melee or ranged attack rolls.

#Character Actions additional rulings:
##Whenever someone’s Actions are still unused due to delaying his or her action until any time later in the round to see what the other characters intend to do, they can also be used up as Reactions.
##As per the usual BESM D20 rules, there are no attacks of opportunity (and as such, plenty of feats that increase the number of Attacks of Opportunity are deemed useless), though being attacked while performing actions that makes the attacked target particularly vulnerable to attacks might still subject itself to a circumstances penalty to AC.
##It is obviously possible to only partially use a Move Action to Move to some of the speed that the character can take and then, later on, use up the remaining part of it.
##When acting at the same time, Actions that use up fewer Actions are executed first, allowing to interrupt actions that require concentration or to kill/disable others first.
##Readying Actions make lets the character act first, also directly allowing to interrupt actions that require concentration or to kill/disable others first.


##############################################
#PHYSICAL STAMINA IN COMBAT

Physical Stamina in Combat:
##Light combat (evaluation is based on the creature’s physical capabilities) uses up stamina as if the creature is moving at Hustling pace and, as far as getting fatigued is concerned, the effects of those two effect categories stack with each other.
##Taxing Combat (evaluation is based on the creature’s physical capabilities): uses up stamina as if the creature is moving at Running pace and, as far as getting fatigued is concerned, the effects of those two effect categories stack with each other.

##############################################
#HANDLING REGENERATION ATTRIBUTE
Considerations regarding the Extraordinary Monster Ability „Regeneration“:
The Extraordinary Monster Ability „Regeneration“ is usually acquired as variant version of the Regeneration Attribute and uses the Standard DnD3.5 Regeneration rules in which ineffective forms of health point damage are converted into Nonlethal health point Damage. Obviously, creatures with this form of Regeneration don‘t convert excessive Nonlethal health point Damage into Lethal health point Damage as long as it isn’t from some type of Nonlethal damage that their Regeneration is unable to restore, i.e. anything that bypasses their Regeneration as well as any Nonlethal Damage due to starvation, thirst or suffocation. Creatures can only acquire this kind of Regeneration if the bypass requirements are creature-compatible (i.e. the bypass requirements of have to make sense for the creature in question based on its overall characteristics).

#Pricing of the Extraordinary Monster Ability „Regeneration“
##Pricing of the Extraordinary Monster Ability „Regeneration“ with only one weakness when acquired through Regeneration Attribute: 6CP per Rank, with selected weaknesses that that are very broad or particularly narrow affecting the CP per Rank cost further (as such either by reducing the CP costs per Rank in case of very broad weaknesses by half or in case of narrow restrictions by doubling the CP costs per Rank).
##Pricing of the Extraordinary Monster Ability „Regeneration“ with at least two weakness when acquired through Regeneration Attribute: 3CP per Rank, with selected weaknesses that that are very broad or particularly narrow affecting the CP per Rank cost further (as such either by reducing the CP costs per Rank in case of very broad weaknesses by half or in case of narrow restrictions by doubling the CP costs per Rank).


##############################################
(Attack Rolls for Spells and Special Abilities, etcetera)
Simplified:
All attack-like actions/events that could theoretically be evaded or mitigated in some form or another by “simply moving out of the way"/"Dodging"/"Instantly leaving the affected
area" - i.e. all types of melee attacks/melee touch attacks/ranged attacks/ranged touch attacks or that attacking effects that otherwise require its targets to perform
a reflex save to mitigate at least some of the initial effect - as well as everything else that could be considered as such (like the effects of various attack-type traps or falling
objects) should all involve attack rolls. For cases where this isn’t appropriate, like several types of sudden natural disasters (as well as various types of suddenly appearing hazards
of natural or technological or supernatural origin), Game Masters should instead simply provide a Reflex Save DC to mitigate the effect and should, if the Saving Throw Result surpasses
the Reflex Save DC by at least 10, allow to use up one Unused Action/Delayed Action/Reaction to attempt to move out of the affected area in time to stay unharmed.

When attacking multiple targets (be it as multi-target effect or as AOE effect), the attacker makes one attack roll against all targets. Obviously, all
those attacks can subject each targets to critical hits, with the confirmation roll, should the original roll threaten a critical hit, being handled the same way as #
the original roll. When it comes to AOE attacks, instead of performing multiple attack rolls, its recommended to simply perform one attack roll against all targets in the affected
area. If the attack roll isn’t sufficient to hit any of the affected targets, it is necessary to perform a second attack roll against the general area
(typically against AC 5) to determinate if the attack at least managed to hit the targeted area.

#Overview for Single-Target or Multi-Target Attack-like actions/events:
###Attack Misses: The target is - usually - unaffected.
###Attacks Hits and successful Dodge/Parry Defence: The target is - usually - unaffected.
###Attacks Hits and successful Block Defence: The damage/effect the target takes is subjected to is reduced accordingly.
###Attacks Hits and Dodge/Parry/Block Defence fails: Target Reflex Save Result to mitigate the initial effect is reduced by half
and the target is otherwise affected as usual. Severe failure of Defence check might involve additional consequences.
###Attack Hits and no defensive Action: Target Reflex Save Result to mitigate the initial effect is reduced by half
and the target is otherwise affected as usual.
###Attack is successful Critical Hit (no Dodge/Parry/Block Defence possible): Target Reflex Save Result to mitigate the initial effect is reduced by half
and the target is also suffering the effects of the Critical Hit, while otherwise being affected as usual.

#Overview for AOE Attacks actions/events:
###AOE Attack Misses and fails to hit the general area the target is located in: The target (as well as the targeted area) isn’t hit by the AOE attack and as such
- usually - avoids the entire part of the effect that required to be hit by the initial attack roll or that otherwise can be reduced through the initial Reflex Save.
###AOE Attack Misses and Reflex Save Succeeds: Target is allowed to use up one Unused Action/Delayed Action/Reaction to attempt to move out of the
affected area in time so that it isn’t hit by the AOE attack and as such - usually - avoids the entire part of the effect that required to be hit by the
initial attack roll or that otherwise can be reduced through the initial Reflex Save.
###AOE Attack Hits and successful Dodge/Parry Defense and Reflex Save Succeeds: Target is allowed to use up one Unused Action/Delayed Action/Reaction to
attempt to move out of the affected area in time so that it isn’t hit by the AOE attack and as such - usually - avoids the entire part of the effect that
required to be hit by the initial attack roll or that otherwise can be reduced through the initial Reflex Save.
###AOE Attacks Hits and successful Block Defence: The damage/effect the target takes is subjected to is reduced accordingly.
###AOE Attacks Hits and Dodge/Parry/Block Defence fails: Target Reflex Save Result to mitigate the initial effect is reduced by half
and the target is otherwise affected as usual. Severe failure of Defence check might involve additional consequences.
###AOE Attack Hits and no defensive Action: Target Reflex Save Result to mitigate the initial effect is reduced by half
and the target is otherwise affected as usual.
###Attack is successful Critical Hit (no Dodge/Parry/Block Defence possible): Target Reflex Save Result to mitigate the initial effect is reduced by half
and the target is also suffering the effects of the Critical Hit, while otherwise being affected as usual.

For most attack types without defined Critical Hit mechanics, at least as long as the GM doesn’t decides otherwise, a critical hit applies on a
natural 20 and inflicts double damage.
################################################## ##############################


################################################## ################################################## ################################################## ###########
CRITICAL HITS, CALLED SHOTS, COUP DE GRACE, ETC.

#Additionally “Threatening a Critical Hit” for all types of attacks (including Called Shots) that involve attack rolls always applies when:
##The Attack successfully hits the target (the attacked target doesn't use/fails its
defense roll, etc.) AND
##the attack roll surpasses the target’s AC that applies against the attack by at least 20 AND
##the attack roll is at least equal to three times the target’s AC that applies against the attack.

#“Critical Called Shot“ effect Minimum Damage Requirement is to inflicting health point damage in one attack that is at least equal to 1/20 of the targeted creature’s Maximum HP.

#„Debilitating Blow“ effect Minimum Damage Requirement is to inflicting health point damage in one attack that is at least equal to half the targeted creature’s Maximum HP AND at least equal to the targeted creature’s constitution score.

#Whenever someone that attempts a Called Shot against any body section expect against the most vital organs - i.e. Called Shots against “the most vital organs” are considered Called Shots with „Debilitating Blow“ effects that can critically damage or even outright destroy any body section (typically the Heart or the Brain or the absolutely critical spinal cord sections on the neck) to such a degree that it would basically result in at least near instant death for the creature in question - and the attack is particularly outstanding in comparison to the task in question, allowing the attacker to cause much harm towards its target with far less force than usual. In such cases, the Minimum Damage Requirement in regard to inflicting „Debilitating Blow“ effects is lowered to at least equal to 20% of the targeted creature’s Maximum HP AND to at least equal to half the targeted creature’s constitution score. The attack is particularly outstanding, if:
##the attack is a successful Critical Hit AND
##the attack roll surpasses the target’s AC that applies against the attack by at least 20 AND
##the attack roll is at least equal to two times the target’s AC that applies against the attack.

#Coup de Grace:
Coup de Graces are changed to one full round-action attack performing a „execution blow“-type Called Shot – which means some attempt to target some absolutely vital location or to attempting to perform some particularly lethal action like crushing the brain, destroying the heart, decapitation or breaking/destroying the neck, etc. - that‘s also performed with an additional +10 circumstances bonus to the attack roll. Every „Execution blow“ functions as two Called Shots combined into one, acting as if both the Heart as well as one other hit location that’s based on in which way the attacker attempts to slay the creature with the Coup de Grace. As such, even if the target manages to survive the Coup de Grace itself, it is not only subject to the side effects of the first Called Shot but also subject to one additional Called Shot effect based on the action that was attempted as Coup de Grace, i.e. attempting to destroy the Heart would still result in a Called Shot against the Chest while attempting to crush the Head would still result in a Called Shot against the Head and attempting to decapitate the creature would still result in a Called Shot against its Neck, etc.. However, it’s important to note that the bonus effects listed as Critical Called Shot effects for Called Shots against the Heart never apply to the Coup de Grace, so in case of a critical hit, only the „Critical Called Shot“ effect consequences of the secondary targeted region (like Chest, Head and Neck) apply.

#Negative Health points: either Negative HP to up to CON score or to up to 1/4 of MAX HP, based whichever of the two values is higher.

#(Critical Hits against Objects/Structures/Massive Structures)
While most Objects and Structures - with some expections like Vehicles, Mechas or various technological devices - aren’t typically affected by Critical Hits,
this doesn’t mean that a particularly well-executed attack is exploit its structural characteristics to deal even more damage.
Additional Requirements:
##The Attack successfully hits the Object/Structure (the attacked target doesn't use/fails its
defense roll, etc.) AND
##the attack roll surpasses the Object’s/Structure’s AC that applies against the attack by at least 20 AND
##the attack roll is at least equal to three times the Object’s/Structure’s AC that applies against the attack.
##the attack roll surpasses the Object’s/Structure’s Structural Armor Rating by at least 20.

Standard Damage Multiplier of Critical Hits against Structures/Objects that aren’t vulnerable against Critical Hits is - regardless of what multiplier would
normally apply - 1.5x.
###############

(Optional)
#Automatic Called Shot (usually to random location) effect for non-“Called Shot“ effects applies to affected creature when either one of the two conditions apply:
##the creature suffers actual health point damage due to being critically hit by some non-called shot effect. However, in this case, the bonus effects listed as Critical Called Shot effects never apply to that hit, so that the consequences are limited to only regular „Called Shot“ effects and „Debilitating Blow“ effects.
##the creature suffers Massive Damage due to being hit by some non-called shot effect. However, in this case, as consequence of the body getting messed on a broader scale, so for every 25% damage equal to the creature’s Maximum HP, this results two Called Shots that affect possibly multiple (either assigned random or decided by the Game Master based on what makes sense; so the Game Master can also make all attacks hit the same specific hit location or limit the hit locations to specific sections of the body of various size like, for example, one specific limb, the torso, the head, around the right shoulder, around the left shoulder, the upper half of the body in general, the right side of the body in general, the left side of the body in general or the lower half of the body in general) hit locations and that make the already inflicted damage of the original hit split evenly among themselves (in case some of those multiple hits hit the same location, then this only increase the damage-based severity of the Called Shot to that location, as their individual effects don‘t stack with other). Any Called Shot that‘s happening due to Massive Damage either uses the Save DC against Massive Damage or the regular Save DC against the Called Shot in question, depending of whichever is deemed more appropriate by the Game Master. It‘s also important to note that the bonus effects listed as Critical Called Shot effects never apply to this „Massive Damage causing hit“, so that the consequences are limited to only regular „Called Shot“ effects and „Debilitating Blow“ effects.

Edit:

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D20 Roll for Attack roll, Defense Roll and Saving Throws:

Characters roll the D20 dice until the result is neither 1 nor 20 while taking note of how many times 1 or 20 was rolled, with that result being the result of the roll. Then they they subtract the amount of times 1 was rolled from the number of times 20 was rolled and multiply it by 20; if the result is negative (i.e. more rolled 1 than 20), then they add the result as penalty to the roll, if the result is positive (i.e. more rolled 20 than rolled 1) then they add the result as bonus to the roll. If the result of an attack roll is positive and sufficiently high to actually be equal or above the target’s AC, then that attack threatens a critical hit.

Edit2:

#MASSIVE DAMAGE

The DnD3.5 Massive Damage Variant Rules as well as Pathfinders Massive Damage Optional Rules are combined and integrated into the BESM D20 rules to handle the general effects of massive physical trauma.

As such, the Massive Damage Threshold for creatures to be subjected to Massive Damage is considered to be equal to [half the creature’s Maximum Health Points and at least equal to the creature’s Constitution score].

A failed save against Massive Damage results in the creature being reduced to a dying state, which means their current HP are automatically reduced to -1 Health points.

Edit3:

Structural Armour (the best type of damage reduction for creatures besides outright immunity) is limited by the creature’s constitution score, with the upper limit being equal to [4x(Constitution Modifier)].

Edit4: put things into spoiler

Edit5: Fixed outdated values for Massive Damage Attribute and Ability Score pricing at higher levels (i.e. to half the CP costs).