Looking for eyes/comments on a 5e D&D fork

[GeneralVryth]

1. I'd assume they can...that's why they get 4 attacks while everyone else is stuck at 2. But maybe?

2. Deflect: Roll when you're attacked. I think? I forget. But if the attack misses, you get to smack back for free.

3. Shield...yeah. Probably.

4. Oathbound & latex...oops. I need to do careful search for all that stuff. I know I want an "avenger" subclass, not sure about the others. Maybe a quite support-focused one?

5. Versatile--eyah. I can see that.

6. Action Surge...I though it did? Currently it's at 3 STA for an extra action. Which is overcosted for a low-level Attack, but...maybe?

7. Hmm. Yeah, About STA + CON...I wanted the pure martials to have lots of extra STA compared to half-casters/full-casters. But numbers aren't right. As for AET...I think I'd rather do recharge mechanics? Like...get X (2*casting mod?) back on a short rest?

8. Thanks! (about true strike). I figured I was going to make it best for the half-casters (ie gish types), so having it be a cantrip was kinda odd. But the old effect just sucked.

1. I get the 4 attack point, also Action Surge. I am not sure anymore. My instinct is Force Jump is a better aesthetic, but that could easily be my own bias. Ultimately as long as the effect and cost are clear, that's what matters.

2. The rules say you have to use deflect before knowing the result, but it doesn't mention anything about it being declared before or after the dice role, or whether you know the role (not the result). This is a pretty important distinction because Deflect only effects 1 attack, and you only get the bonus attack when you create a miss, you need to be confident about its usage as burning 2 STA and your reaction is a lot for no no effect. There is also the thought of how often does it just get used for a free attack and not even helping prevent an attack?

3. Would a simple solution be have it give +1 AC and it can't be used with a physical Shield? It makes it less AC than Shield of Faith, but you can block MM and you get the spending AET option.

4. Isn't something like a Protector Oathbound already a kind of support? Also just based off the Oathbound concept that seems to slot in naturally for characters like loyal bodyguards. What mechanical support effects are you thinking of? as that would quickly help narrow down the theme of a support Oathbound.

5. I stated in a different thread that the real world advantage of something like a versatile weapon is being able to quickly trade off between power and defense. Maybe Versatile specialization should be something like, "When you are wielding a versatile by itself (without a shield, weapon, or other item in your off hand), you get +1 on attack rolls with the weapon, and +1 AC. When attacking with the weapon you can take a -2 penalty to your AC until the start of your next turn to add your proficiency bonus to damage dealt until the start of your next turn." The net effect is you can choose between +1 Atk and +1 AC or +1 Atk, -1 AC, and +Prof Dmg. Playing in to the versatile nature.

6. More importantly I think 3 STA is overcosted for an action that isn't Attack or casting a spell. Just spitballing, what if it was 2 STA, and it gave you a non-Attack action and increased the attacks of your Attack action by 1? That way it becomes less about a brutal alpha strike and becomes more a utility burst, while providing attack benefit?

7. I am not actually sure if it's too much or not, because it's what powers Deflect and that is clearly designed to be more of a core defensive ability. But that only works if it is well balanced so it's good but not so good you only want to use it. Hence my question above. On the AET front, since they are more or less spell points you might find this interesting:

1	4
2	6
3	14
4	17
5	27
6	32
7	38
8	44
9	57
10	64
11	64
12	64
13	64
14	64
15	64
16	64
17	64
18	71
19	80
20	90

That's the spell point progression for full casters in 5e if you remove the 6+ level spell slots. I wonder if there is something to making the AET progression less linear, as it would make the Legendary Effects less of a spike when the casters start getting them.

[PhoenixPhyre]

1. I get the 4 attack point, also Action Surge. I am not sure anymore. My instinct is Force Jump is a better aesthetic, but that could easily be my own bias. Ultimately as long as the effect and cost are clear, that's what matters.

2. The rules say you have to use deflect before knowing the result, but it doesn't mention anything about it being declared before or after the dice role, or whether you know the role (not the result). This is a pretty important distinction because Deflect only effects 1 attack, and you only get the bonus attack when you create a miss, you need to be confident about its usage as burning 2 STA and your reaction is a lot for no no effect. There is also the thought of how often does it just get used for a free attack and not even helping prevent an attack?

3. Would a simple solution be have it give +1 AC and it can't be used with a physical Shield? It makes it less AC than Shield of Faith, but you can block MM and you get the spending AET option.

4. Isn't something like a Protector Oathbound already a kind of support? Also just based off the Oathbound concept that seems to slot in naturally for characters like loyal bodyguards. What mechanical support effects are you thinking of? as that would quickly help narrow down the theme of a support Oathbound.

5. I stated in a different thread that the real world advantage of something like a versatile weapon is being able to quickly trade off between power and defense. Maybe Versatile specialization should be something like, "When you are wielding a versatile by itself (without a shield, weapon, or other item in your off hand), you get +1 on attack rolls with the weapon, and +1 AC. When attacking with the weapon you can take a -2 penalty to your AC until the start of your next turn to add your proficiency bonus to damage dealt until the start of your next turn." The net effect is you can choose between +1 Atk and +1 AC or +1 Atk, -1 AC, and +Prof Dmg. Playing in to the versatile nature.

6. More importantly I think 3 STA is overcosted for an action that isn't Attack or casting a spell. Just spitballing, what if it was 2 STA, and it gave you a non-Attack action and increased the attacks of your Attack action by 1? That way it becomes less about a brutal alpha strike and becomes more a utility burst, while providing attack benefit?

7. I am not actually sure if it's too much or not, because it's what powers Deflect and that is clearly designed to be more of a core defensive ability. But that only works if it is well balanced so it's good but not so good you only want to use it. Hence my question above. On the AET front, since they are more or less spell points you might find this interesting:

That's the spell point progression for full casters in 5e if you remove the 6+ level spell slots. I wonder if there is something to making the AET progression less linear, as it would make the Legendary Effects less of a spike when the casters start getting them.

2. Ah. If it's before knowing the result, then my standard (and I should be more clear) is that you generally see the rolls. I roll in the open for my games. One note is that masterwork armor (which is expensive but not out of reach or magical, although some magical armor is masterwork) drops the cost in half for medium/heavy armor.

3. I was thinking actually of going towards more of a "creates a ward, like the abjurer's one, that protects you from concentration checks as long as it lasts". And then a higher-level one that creates a bubble around you that eats damage for a group. I really want to stay away from boosts to AC, especially stacking ones.

4. As I see it, the current one (Devotion) is a balanced, "good guy" oathbound. Oathbound are more toward the support end anyway naturally. Avenger would be more offensive, and then maybe a Protector (tanky/sticky) and a ???? (more focused on buffing/healing).

5. I'm not sure. I'll have to think about it. I might just remove the whole versatile thing entirely, including the base property. It's just not something that has good resonance for me. Dunno.

6. Yeah. That one's hard to balance. What you're proposing, to be clear, is "you can take an additional action as long as it's not the Attack action; if you take the Attack action on this turn, you can make an additional attack with it?" (Ie they have to choose N+1 attacks OR two non-attack actions?) That's an idea. I'll think about it.

7. I'm actually trying to tone down the resource progression of casters. Quite a lot. Especially their rate of growth. That nonlinearity, combined with the non-linear growth of power of individual spells, is exactly why casters are so "quadratic" (it's actually more like L^4 once you sit down and look at it). And that irks me, because it inherently breaks stuff. I'm going for roughly logarithmic overall power growth. Fast at first, then slowing down and becoming more horizontal at higher levels. Legendary Effects are 1x/day each, and most full casters will know 5 of them total. They don't cost AET and are really really hard to stop (their AET-cost equivalent for things like dispelling and countering is fixed at 5+level).

[stoutstien]

For versatile weapon mastery you could get a bonus to your first attack if you are wielding only that weapon vs a target due to the unpredictability of being one or two handed attacks?

For second wind it wouldn't be the worst Idea to have a line for when somebody wants to dump their sta prior to a rest into this healing to enhance the normal healing from said rest rather than it just spamming it.

[Notafish]

My 2cp/select first impressions. I have not done a systematic read-through; I'm mostly just poking around the html documents right now.

• This is very impressive and well-thought-out. I especially like the clarity in the rule descriptions and the meta-commentary on the design intent behind many changes and rules, as well as the way your "magic all the way down" approach to worldbuilding is explained in the introductions

• I love the Arcanist class compared to vanilla 5e's sorcerers and wizards.

• I also like the change to spellcasting that seems to make all casters essentially work off of spells prepared.
• Since I think this change applies to all casters, it is confusing that some class tables mention "spells known" as opposed to simply "spells", which is confusing.

• Also, the "Book Mage" heading on the html document is one level lower than I think it should be (h4 instead of h3).

• I like the idea of having more mechanical variation between weapons, but I don't really like the Battering property, given that AC is still an amalgamation of dexterity and armor thickness. Making the damage-on-miss scale with proficiency rather than Strength also feels a little wacky in that it might make wielding a battering weapon an appealing option for characters dumping physical ability scores.

• I might struggle to teach/use the STA and AET systems with my usual groups and would likely need to provide some custom reference materials to remind folks of their options.

• When you spend AET to Focus, does this only apply to checks where you have Proficiency already?

• Like I said above, I like a lot of this, but even if I don't wind up running a game with this system, I absolutely plan to reference the XP/Advancement chart in the future. At the very least.

[PhoenixPhyre]

My 2cp/select first impressions. I have not done a systematic read-through; I'm mostly just poking around the html documents right now.

• 1. This is very impressive and well-thought-out. I especially like the clarity in the rule descriptions and the meta-commentary on the design intent behind many changes and rules, as well as the way your "magic all the way down" approach to worldbuilding is explained in the introductions

• 2. I love the Arcanist class compared to vanilla 5e's sorcerers and wizards.

• 3. I also like the change to spellcasting that seems to make all casters essentially work off of spells prepared.
• Since I think this change applies to all casters, it is confusing that some class tables mention "spells known" as opposed to simply "spells", which is confusing.

• 4. Also, the "Book Mage" heading on the html document is one level lower than I think it should be (h4 instead of h3).

• 5. I like the idea of having more mechanical variation between weapons, but I don't really like the Battering property, given that AC is still an amalgamation of dexterity and armor thickness. Making the damage-on-miss scale with proficiency rather than Strength also feels a little wacky in that it might make wielding a battering weapon an appealing option for characters dumping physical ability scores.

• 6. I might struggle to teach/use the STA and AET systems with my usual groups and would likely need to provide some custom reference materials to remind folks of their options.

• 7. When you spend AET to Focus, does this only apply to checks where you have Proficiency already?

• 8. Like I said above, I like a lot of this, but even if I don't wind up running a game with this system, I absolutely plan to reference the XP/Advancement chart in the future. At the very least.

1: thanks! One of my big intents was to be more explicit about my underlying assumptions. Because I think 5e doesn't do a good job in doing so, which makes a bit of a mess.
2. Yay! That one I've been worried about. Anything in particular you like?
3. Yeah, they're all "spells prepared", kinda cleric style. Because teaching people the whole known/prepared/sorta-prepared distinction got really old, really fast.
3a. I do need to clean that up.
4. Oops. The heading styles are kinda all over the place in a lot of places, I think.
5. That's a decent idea (STR not proficiency). I'll consider it. Thanks! Battering is a rip-off of one of 4e's features. The idea is that you hit so hard that even on a notional miss (like a deflection/parry), you still hurt people. I could make it more fiddly (ie miss but only because of armor, rather than dex), but I'd rather not.
6. Generally, AET and STA are spent on
a) class features
b) skill tricks
c) the four "generic" actions.

What particularly is confusing? Can I word it/explain it better? Given time, I may make a basic chart...

7. Both Focus and Exert apply to any check that uses the appropriate ability score. The idea is that you can choose to succeed (or at least drastically increase your chances of success)...at a resource cost. So if you don't have proficiency, you have proficiency for that check. If you do have proficiency, you have expertise. If you have expertise, you have 3x proficiency.

8. That's actually something I've been running in my regular 5e games for a while now. I've found that stabilizing at 1 level/4 sessions is just about right for me. I tried stabilizing at 3 sessions, but that was too fast. Hard to learn your character and do meaningful things in that window.

[Notafish]

2. Yay! That one I've been worried about. Anything in particular you like?
6. Generally, AET and STA are spent on
a) class features
b) skill tricks
c) the four "generic" actions.
What particularly is confusing? Can I word it/explain it better? Given time, I may make a basic chart...

2. (Arcanists) - I like the shared access to metamagic regardless of origin, and I think that using fungible points (AET, MP, Ki, what have you) (or memorized repeatable things like your incantations) is easier to map to imaginary spellcasting, outside of casting using countable Things like scrolls or cards. The ability to choose between a few big effects (that cap out at "impressive" rather than "worldbreaking") or lots of smaller options also seems more fun to me than expending spell slots.
I do admit that it seems a bit odd for the Book Mage to be able to swap the spells in their spellbook, but it is not immersion-breaking for me - I just figure the access to the extra reference material lets them have more spells prepared. Also, on second read-through, I noticed that the Book Mage does not have any specific Ritual/Incantation-related features, but they do have a note about getting access to "Ritual Caster". I do think that it would be nice to have that option - If I were playing a Book Mage, could I have the option to trade an extra prepared spell for an Incantation of appropriate level scribed into the spellbook?

6. (AET and STA) - for myself, I found a need to check several times what the refresh rate (short vs. long rest) was for the different resources. STA on Short rest, AET on Long rest is easy enough to memorize, but I can imagine needing an end-of-rest sequence to make sure the appropriate resources were spent or refreshed, as well as a basic reference for the action options and costs (and some "spell cards" for referencing the costs/effects of features, spells, and skill tricks, but that's no different from what I want for other WotC DnD). In the teach, I'd probably want to present some recommendations for easing the strain of book-keeping, just to emphasize the shift from counting slots and feature uses to tallying points. All characters needing to track HP, STA, and AET is just complex enough that I might try rigging up a player reference sheet rather than trusting everyone to read the rules and coming up with a tracking system on their own.

[PhoenixPhyre]

2. (Arcanists) - I like the shared access to metamagic regardless of origin, and I think that using fungible points (AET, MP, Ki, what have you) (or memorized repeatable things like your incantations) is easier to map to imaginary spellcasting, outside of casting using countable Things like scrolls or cards. The ability to choose between a few big effects (that cap out at "impressive" rather than "worldbreaking") or lots of smaller options also seems more fun to me than expending spell slots.
I do admit that it seems a bit odd for the Book Mage to be able to swap the spells in their spellbook, but it is not immersion-breaking for me - I just figure the access to the extra reference material lets them have more spells prepared. Also, on second read-through, I noticed that the Book Mage does not have any specific Ritual/Incantation-related features, but they do have a note about getting access to "Ritual Caster". I do think that it would be nice to have that option - If I were playing a Book Mage, could I have the option to trade an extra prepared spell for an Incantation of appropriate level scribed into the spellbook?

6. (AET and STA) - for myself, I found a need to check several times what the refresh rate (short vs. long rest) was for the different resources. STA on Short rest, AET on Long rest is easy enough to memorize, but I can imagine needing an end-of-rest sequence to make sure the appropriate resources were spent or refreshed, as well as a basic reference for the action options and costs (and some "spell cards" for referencing the costs/effects of features, spells, and skill tricks, but that's no different from what I want for other WotC DnD). In the teach, I'd probably want to present some recommendations for easing the strain of book-keeping, just to emphasize the shift from counting slots and feature uses to tallying points. All characters needing to track HP, STA, and AET is just complex enough that I might try rigging up a player reference sheet rather than trusting everyone to read the rules and coming up with a tracking system on their own.

2. Hmm...I thought I'd given the Book Mage some incantation features...probably an oversight. I'd personally be fine with trading one prepared spell for a similar-strength incantation.

6. Yeah, that makes sense. I think having a good character sheet with the recharges in the boxes would go a long way. I'm horrible at graphic design for such things, so I've been putting off making such a sheet.

[PhoenixPhyre]

How does this sound for shield:

Shield
2 AET, 1 action, self, VS, 10 minutes.

An invisible barrier of magical force appears and protects you. This barrier has 10 hit points. Whenever you would take damage and the barrier is active, the barrier takes the damage instead, reducing its hit points. If the barrier absorbs all the damage, you do not need to make Concentration saves if you are concentrating on a spell or ability. You take any damage in excess of the barrier's hit points, which provokes Concentration saves as normal. When the barrier is reduced to zero hit points, the spell ends.

In addition, you are immune to the magic missile spell as long as the barrier is active.

Overcast When you cast this spell using more than 2 AET, the barrier's hit points increase by 5 for every additional AET spent.

Effectively, it's THP but better (stacks with THP, but prevents losing concentration). Limited amounts though. Not sure how much of a barrier is
a) enough that it's worth casting but
b) not so much that it's a "yup, always going to have that up" or "must pick" spell.

[stoutstien]

How does this sound for shield:

Shield
2 AET, 1 action, self, VS, 10 minutes.

An invisible barrier of magical force appears and protects you. This barrier has 10 hit points. Whenever you would take damage and the barrier is active, the barrier takes the damage instead, reducing its hit points. If the barrier absorbs all the damage, you do not need to make Concentration saves if you are concentrating on a spell or ability. You take any damage in excess of the barrier's hit points, which provokes Concentration saves as normal. When the barrier is reduced to zero hit points, the spell ends.

In addition, you are immune to the magic missile spell as long as the barrier is active.

Overcast When you cast this spell using more than 2 AET, the barrier's hit points increase by 5 for every additional AET spent.

Effectively, it's THP but better (stacks with THP, but prevents losing concentration). Limited amounts though. Not sure how much of a barrier is
a) enough that it's worth casting but
b) not so much that it's a "yup, always going to have that up" or "must pick" spell.

Numbers would need adjusting but I think it would work. Scaling anything that deals directly with HP is difficult. Although within your changes anything that protects concentration is much more difficult to obtain so who knows.

I would also add a line about how any type of damage mitigation that you might have doesn't affect this barrier. For example if you have fire resistance and get hit by a fireball the barrier doesn't have fire resistance.

[PhoenixPhyre]

v1.1 is now released!

new PDF @ https://github.com/bentomhall/nih-sy....0/NIH.1.1.pdf

Many small changes. Primary large ones:

Added html version: https://admiralbenbo.org/homebrew/nih/index.html, including lots of prettification.
Lotsa cleanup on formatting and stupid mistakes.
Nets are now equipment, not weapons, and require saves, not attacks.
Added "exotic ranged weapons", which subsumes all the thrown, attack-based consumables. Reworked their effects.
Rogue now has 2 subclasses--the very magical Shadowdancer and the less magical Trickster.

[stoutstien]

Looking good. Compiling feedback. Got distracted with CWN release and table wanted to do a few one shots of that before going back to yours.

[Yakk]

The "tiers" via spell levels can be used as an organizing principle.

When spells cost 1 to 15 units, that means you have 15 tiers. If you replaced it with 5 tiers costing 1, 3, 5, 9 and 15, both players *and designers* have less categories to worry about.

A secondary advantage, from my perspective, is you can co-measure another game feature you have, namely skill tricks. You have 4 categories of skill tricks.

Imagine 5 tiers of both, gated:
Tier 1: L 1-3 (or 4 to maintain pattern of 4 levels of each, but I sort of like 3).
Tier 2: L 4-8
Tier 3: L 9-12
Tier 4: L 13-16
Tier 5: L 17-20

All that this asks of you is that when you design spell power levels, you *round them*, or you fit them into a wider bucket. And because 14 vs 15 unit of power is a kind of false precision, this should improve your ability to design, and improve the ability for people to learn your design.

You can use adjectives for the 5 tiers, but I'm uncertain why. With 2 systems with 5 levels in each, designed to unlock at similar levels, and with your player base accustomed to D&D (which they will be) spells, it should be clear.

Under this, you'd have 5 levels of Skill Tricks, and 5 levels of Spells. And it is mostly a relabelling.

Keeping the Aether at the core, upcasting would still be just providing more Aether to your spell.

[PhoenixPhyre]

The "tiers" via spell levels can be used as an organizing principle.

When spells cost 1 to 15 units, that means you have 15 tiers. If you replaced it with 5 tiers costing 1, 3, 5, 9 and 15, both players *and designers* have less categories to worry about.

A secondary advantage, from my perspective, is you can co-measure another game feature you have, namely skill tricks. You have 4 categories of skill tricks.

Imagine 5 tiers of both, gated:
Tier 1: L 1-3 (or 4 to maintain pattern of 4 levels of each, but I sort of like 3).
Tier 2: L 4-8
Tier 3: L 9-12
Tier 4: L 13-16
Tier 5: L 17-20

All that this asks of you is that when you design spell power levels, you *round them*, or you fit them into a wider bucket. And because 14 vs 15 unit of power is a kind of false precision, this should improve your ability to design, and improve the ability for people to learn your design.

You can use adjectives for the 5 tiers, but I'm uncertain why. With 2 systems with 5 levels in each, designed to unlock at similar levels, and with your player base accustomed to D&D (which they will be) spells, it should be clear.

Under this, you'd have 5 levels of Skill Tricks, and 5 levels of Spells. And it is mostly a relabelling.

Keeping the Aether at the core, upcasting would still be just providing more Aether to your spell.

Strong disagree. It's exactly the rounding process that screws everything up. Having more flexibility in spells means that you can tune those much more freely to actually have a system that works, unlike D&D spellcasting, which is broken on all levels. Spell "levels" is a horribly horribly confusing, horrible design from the get go because it means you have to shove things into ill-fitting bins.

Similar things should be similar. Different things should be different, because forcing them into the same bins causes everything to break. Or at least makes things muddy. In principle, I'd expect a "fully featured" system to have spells and abilities at every aether cost between 0 and 15+

Sorry, but saying I should go back to spell levels and have them come on at specific points is exactly the kind of thing that counts as "you should scrap this and do something else entirely." (AKA not a piece of useful feedback IMO). It's a fundamental refactor of the entire thing, and involves diving back into the mud that is at the core of my dissatisfaction with D&D spellcasting.

And I question the idea that it's harder to write down "this spell costs 5 and that one costs 7" compared to having fewer buckets. Each spell is its own thing. You already have many other packets of abilities that cost varying amounts, so tying everything to 5 fixed numbers means that the whole aether concept is unnecessary.

[Yakk]

Monsters:

I find making monsters recharge at the end of their turns is better than at the start of their turn.

So Breath Weapon (Recharge 56) means that at the end of its turn, the players get a chance to learn "oh, it is inhaling to breathe fire again".

You could attach a perception DC to it, but I dislike the extra rolling.

A second rule is that Legendary Actions if they are attack rolls have Advantage against the enemy who just went, and if they impose saving throws those saving throws are at Disadvantage. You can instead change it to disadvantage IF NOT the enemy who just went.

The goal is to provide a strong mechanical incentive for Legendary actions to be reactive and spread out, instead of focused (which D&D-esque combat engine strongly encourages). It also means that team PC has a maximum amount of time to help with the consequences of Legendary actions. (Really, the optimal use of legendary actions is to knock a PC out of combat for that turn BEFORE that PC goes; targetting the PC that just went is the worst option. By rewarding it mechanically, we take the otherwise worst option and make it fun, and improve the dynamics of combat as "the PC attacks the dragon", "the dragon swats the PC" is great dynamics.)

...

CR calcuation. If you are redoing CR, you might as well make it Level instead of CR based.

With level based, you add up the PCs levels (possibly fudged, like "# of PCs plus total PC levels") and you compare it to the sum of monsters levels (plus 1/2 the number of monsters), instead of comparing CR to (PC levels/4) or whatever.

Offensive Level = DPR/3 - 1
A 3 DPR creature has an offensive level of 0. (CR 0 to 1/8)
A 6 DPR creature has an offensive level of 1. (CR 1/2 ish)
A 9 DPR creature has an offensive level of 2. (low CR 1)
A 12 DPR creature has an offfensive level of 3. This is roughly CR 1
So a 123 DPR creature has an offensive level of 40 (CR 20).

Now, accuracy also contributes. Because I want proficiency bonus to be injected *at the end* of the system, we should subtract it out and only care about your *offensive stat modifier*(s). The expected offensive stat modifier goes from +0 to +3 in your system (over 40-ish levels), and 2 points of it are worth a full offensive CR.

So over 40-ish levels, we get +1.5 to difficulty rating from offensive stat, or like 4% impact. We'll have to handle it to properly zero the scale, but on a per-level basis it is noise.

Note that the general map for offensive CR to level is roughly CR*2+1, with tiny differences; your chart is similar enough to the DMG.

For defensive CR, you'll note that it is for the most part (HP/15-1.5); percentage wise there is error, but it isn't that large.

Using Level = CR*2+1, if CR=(HP/15-1.5) then Level = (HP/15-1.5)*2+1 = HP/7.5 -2 as a first approximation.

AC is bigger here, and we don't use proficiency on AC. It goes up by 6 to 7 (depending on what we use as our starting point) over 40-ish levels (20-ish CR), and is worth an impact of 3ish CR - 15%, quite substantial. We can use this to decrease the price of HP by 1/.85, or

Level = HP/9 + AC - 15

Plugging in level 10 we get 175 HP and 17 AC:

175/9 + 17-15 = 21.444, which is pretty close to the (CR*2+1) we are aiming for

The real trick at this point is to calibrate the "Level 1" point, especially if you want monsters to be additive (ie, throw X L1 monsters instead of 1 L20 monster). By the time you hit level 20, the DM will know "ok, the party is performing 50% over expectation".

There are linearity constraints here that are tricky.

Regardless, what this would do is that for a party of 4 L 8 PCs, throwing 4 L 8 monsters should have a known difficulty scale - and upping (or lowering) the monster levels a known effect. Ie, make the baseline assumption multiple monsters (roughly equal to number of PCs), and scale things from there. (This is 4e encounter building).

We then can look at elite (superior, "wider" monsters) and minion (weaker monsters, more numbers).

For elite, if you take a monster and give it 2x HP and +50% damage, the damage it does compared to two normal monsters (where the PCs focus fire one down) over a fight is similar. In fact, (Nx HP) and (2+N)/2 x damage does this for an elite replacing N normal monsters.

Status effect shutdown is more effective against the elite. AOE against the swarm is more effective, but if you properly budget it that isn't a huge issue (a fireball that hits K creatures is worth (K+2)/2 times as much damage).

For status effect shutdown, something like legendary resists can be used. But I like the effect of legendary actions. So I would propose combining them.

When you take a legendary action, you can choose to shrug off an effect instead of taking the action. You make a saving throw with advantage against the effect, and on success end it.

Now, status effect shutdowns are still useful, as they consume monster legendary actions. Higher DCs are useful, because they give you a chance to require more than 1 save.

The power budget of legendary action also becomes clear -- 1/2 of the standard action power budget.

And we now get Elite monsters. An Elite(N) monster has Nx the HP of a normal monster, gets N legendary actions, with each Legendary action having a damage budget of 3/2 * (offensive level+1). Legendary Actions are used after a hostile creature's turn, and attacks on that hostile creature are at advantage for a Legendary Action, and saves against the Legendary Action are at disadvantage.

If a creature starts its turn with Legendary Actions, it can proceed to use any remaining ones to save against remaining effects. This is mainly useful if the creature is facing fewer foes than it has Legendary Actions.

An Level K Elite(N) monster is about as dangerous as N level K monsters.

...

We could use similar mechanics for minions. But I like using lower level monsters for that.

...

What remains is the non-linear problem. A level 20 monster (offensive and defensive) has almost 2x the HP and damage of a level 10 monster. Adding up monster levels doesn't quite work.

Ignoring AOEs and CC, the problem is a triangle sum. 5 monsters being focused fired down at a rate of 1/round deal 5*6/2=15 rounds of damage, while a 5x HP/DPR monster deals 25; if the first monster has a 50/50 chance to die before it goes, this becomes exactly half the damage that the bigger monster did. It is comparing the area of a triangle to a rectangle.

As you approach "everyone dies in one round", the damage of the 5 monsters approaches that of the bigger one: the triangle approximates being a rectangle. As you approach "it takes multiple rounds to kill each smaller monster", the total damage of the smaller monsters approaches 1/2 that of the larger one: the triangle becomes perfect.

Defensive level doesn't have this same issue. In fact, having too much defensive level is a slog - we want total defensive level (divided by average PC level) to measure how many PC rounds it takes for the monsters to drop, a real-life table time problem (and not a game balance one).

In essence, as the number of PCs increases, we want defensive level to go up *slower* (keeping total table time bounded) and offensive level go up *faster* (to compensate for focus fire and compensate for lower defensive level in terms of challenge) I think. At the same time, we want to keep the ceiling on per-monster offensive level from growing without bounds (if you look at the elite mechanics, that does it).

For minions, if we have a monster at 1/2 PC level its effective defensive level is 1/2, but its offensive level is somewhere between 1/4 and 1/2 what it claims, as half of them won't last long enough to do its damage budget over a fight.

Should we compare monster defensive level to PC total offensive level to figure out how splattable they are, and use that? Or is there a shortcut?

Anyhow, I don't know if you care about this kind of thinking. Some people consider it a waste, because 5e encounter building and fudging it is usually enough. So I'll stop.