Martial PrCs

[NigelWalmsley]

It can be generally acknowledged at this point that the martial classes in 3e kind of suck. The Fighters, Barbarians, and Rangers of the world not only don't keep up with spellcasters at high levels, they fail to keep up with the challenges they can expect to face, or the basic standards of character competence we might expect from them. But there are a lot of characters we'd like to be able to play that are recognizably martial and are entirely able to rise to these standards. The PrCs in this thread are an effort to bridge that gap by creating things that take a standard martial character and allow them to keep pace with spellcasters (at reasonable levels of optimization, at least) into the mid and high levels, just as they do at low levels.

A note on power level: my goal here is to create PrCs, and by extension characters, that can be played at the level of a competent spellcaster without rules-lawyering or dumpster-diving. As such, these things are almost certainly overpowered when compared to existing PrCs, or existing martial characters. That's the point. That said, my design process is not as rigorous as it could be, or like even as it should be. So it's possible that these classes will overshoot that mark and need to be toned down. But please try to keep in my the expected power targets.

Prelude concluded, here are the first two I've written up:

Dragon Aspirant
It's a killing machine the size of a house. Why wouldn't I want to learn its secrets?

Dragons are among the most powerful creatures in the world. It is no surprise that many among the moral races aspire to emulate their power. Among them are warriors who bind themselves to draconic mentors, gaining potent draconic magics. Some work as servants of the dragons who teach them, while others bend their draconic knowledge to their own ends.

BAB: +4
Skill: Knowledge (Arcana) 7 ranks, Intimidate 7 ranks
Special: Must speak Draconic
Special: Must be proficient with a martial weapon
Special: Must have made friendly contact with a dragon of the type she chooses as her patron

Hit Die: d12
Class Skills: The dragon aspirant's class skills (and the key ability for each skill) are Concentration (Con), Craft (Int), Bluff (Cha), Diplomacy (Cha), Intimidate (Cha), Knowledge (arcana) (Int), Profession (Wis), Ride (Dex), and Spellcraft (Int).
Skill Points: 6 + Intelligence bonus

Level	BAB	Fort	Ref	Will	Special	Spellcasting
1	+1	+2	+2	+2	Draconic Patron, Sphere, Armored Mage	+1 level of arcane spellcasting class
2	+2	+3	+3	+3	Draconic Attributes +2	+1 level of arcane spellcasting class
3	+3	+3	+3	+3	Draconic Scales	+1 level of arcane spellcasting class
4	+4	+4	+4	+4	Sphere	+1 level of arcane spellcasting class
5	+5	+4	+4	+4	Improved Sphere Access	+1 level of arcane spellcasting class
6	+6/+1	+5	+5	+5	Draconic Attributes +4	+1 level of arcane spellcasting class
7	+7/+2	+5	+5	+5	Sphere	+1 level of arcane spellcasting class
8	+8/+3	+6	+6	+6	Draconic Durability	+1 level of arcane spellcasting class
9	+9/+4	+6	+6	+6	Improved Sphere Access	+1 level of arcane spellcasting class
10	+10/+5	+7	+7	+7	Draconic Attributes +6, Sphere	+1 level of arcane spellcasting class

Weapon and Armor Proficiency: The dragon aspirant gains proficiency with medium armor and all martial weapons.

Spellcasting: Every level, the dragon aspirant casts spells (including gaining any new spell slots and spell knowledge) as if she had also gained a level in an arcane spellcasting class she had previous to gaining that level. If the character does not have any levels in any arcane spellcasting classes when she takes her first level of dragon aspirant, this class feature gives her levels in sorcerer spellcasting.

Draconic Patron: The dragon aspirant devotes herself to the study of one type of dragon. At 1st level, she chooses one type of chromantic dragon (black, blue, green, red, or white) as her draconic patron. This determines what spheres she has access to. She gains each of the class skills her patron dragon has access to as a class skill. If she would gain a class skill she already has, she instead gains Skill Focus in that skill as a bonus feat.

Sphere: The dragon aspirant gains basic access to a Sphere at 1st level and every three levels thereafter. If the dragon aspirant selects a sphere that she already has basic access to, she upgrades it to advanced access. If she already had advanced access, she gains expert access. The set of spheres the aspirant can select from is determined by her draconic patron. All aspirants can choose the Dragon* or Terror spheres.

A black dragon aspirant can also choose from the Acid*, Corruption*, and Venom spheres.

A blue dragon aspirant can also choose from the Electricity*, Illusion*, and Weather* spheres.

A green dragon aspirant can also choose from the Acid*, Plant*, and Seduction spheres.

A red dragon aspirant can also choose from the Fire, Pyre, and Seduction spheres.

A white dragon aspirant can also choose from the Cold, Frost, and Weather* spheres.

*: New Sphere.

Armored Mage: The dragon aspirant ignores the arcane spell failure chance of any armor or shield with which she is proficient.

Draconic Attributes: At 4th level, the dragon aspirant gets a +2 racial bonus to strength, constitution, and charisma. At 6th level, this improves to a +4 bonus. At 10th level, it improves again to a +6 bonus.

Draconic Scales: At 3rd level, the dragon aspirant's skin begins to turn into scales. she gains a +1 natural armor bonus. This bonus increases by one for each dragon aspirant level she gains thereafter (so a 7th level dragon aspirant would have a +5 natural armor bonus).

Improved Sphere Access: At 5th level, the dragon aspirant's access to her spheres improves. she can choose a sphere she has basic access to and upgrade it to advanced access, or a sphere she has advanced access to and upgrade it to expert access. she cannot use this ability to gain access to a new sphere. At 9th level, she can upgrade her access to another sphere in this way.

Draconic Durability: At 8th level, the dragon aspirant gains the durability of a dragon. she gains DR 15/magic. If she ever becomes an epic character, this DR improves to 15/epic.

New Spheres

Acid
Special: You gain Immunity to Acid.
1st: acid arrow
3rd: acid storm (SpC)
5th: dispel magic
7th: orb of acid (SpC)
9th: acid sheath (SpC)
11th: acid fog
13th: Persistent Maximized acid arrow
15th: Quickened orb of acid (SpC)
17th: acid fog, each creature in the fog is subjected to a targeted greater dispel magic when it takes damage
19th: disjunction

Corruption
Special: You gain immunity to disease.
1st: darkness
3rd: ghoul touch
5th: stinking cloud
7th: black tentacles
9th: Quickened fengut
11th: eyebite
13th: creeping doom
15th: avascular mass (SpC)
17th: Empowered horrid wilting
19th: Quickened cloudkill

Dragon
Special: You can use detect magic at will. This effect also detects mundane wealth as if it was a magic item with a caster level of 1 per 1,000 GP.
1st: blood wind (SpC)
3rd: dragon's breath*
5th: greater magic fang (Dra)
7th: wings of flurry (RoD)
9th: lesser dragon ally (Dra)
11th: primal hunter, primal instinct, primal senses, and primal speed, cast separately (DM)
13th: hiss of sleep (Dra)
15th: animate breath, treats your size as colossal (Dra)
17th: shapechange, dragons and reptiles only
19th: greater dragon ally (Dra)

Electricity
Special: You gain Immunity to Electricity.
1st: lightning bolt
3rd: seeking ray (PHBII)
5th: chain lightning
7th: orb of electricity (SpC)
9th: ball lightning (SpC)
11th: call lightning storm
13th: stun ray (SpC)
15th: stormrage (SpC)
17th: Directing your ball lighting, calling lightning with call lightning storm, and launching bolts from stormrage are free actions that can be taken once each per round
19th: Quickened Maximized chain lightning

Illusion
Special: You can use ventriloquism and ghost sound at will.
1st: silent image
3rd: mirror image
5th: major image
7th: phantasmal killer
9th: mirage arcana
11th: permanent image
13th:project image
15th: simulacrum, you must still have a piece of the creature
17th: wierd
19th: Quickened phantasmal killer

Plant
Special: You can speak with plants as if under the effect of speak with plants.
1st: entangle
3rd: kelpstrand (SpC)
5th: plant growth
7th: command plants
9th: wall of thorns
11th: minor creation (as a standard action)
13th: Greenbound summon monster VII (animals only)
15th: control plants
17th: deadfall
19th: shambler

Weather
Special: You can use gust of wind at will.
1st: obscuring mist
3rd: sleet storm
5th: great thunderclap (SpC)
7th: solid fog
9th: control winds
11th: whirlwind
13th: control weather
15th: Quickened telekinesis
17th: meteor swarm
19th: storm of vengeance

*: New Spell.

Sources Used
Dra: Draconomicon
DM: Dragon Magic
SpC: Spell Compendium
RoD: Races of the Dragon

New Spell
Dragon's Breath
Evocation
Level: Sor/Wiz 2
Components: V, S
Casting Time: 1 standard action
Range: See text
Area: See text
Duration: Instantaneous
Saving Throw: Reflex half
Spell Resistance: Yes

You breath out a blast of energy. You deal 1d6 damage per caster level (no cap) of your choice of acid, cold, electricity, or fire damage. You can choose to have this spell effect a cone (in which case it has an area of 5ft per caster level) or a line (in which case its area is 5ft wide and 10ft long per caster level).

Spoiler: Author's Notes

Show

This class is influenced heavily by the Conduit of the Lower Planes from the Tome of Fiends. Obviously it uses the same Spheres mechanic, and it also has a similar life path of transitioning you out to other PrCs by granting Sorcerer casting. Honestly, you could refigure it to be a base class pretty easily (though in that case you'd want to give it Magical Training as a capstone, rather than have it advance Sorcerer casting). Compared to the Conduit, you get slightly more spheres, but with a much tighter focus (and less use of low-level SLAs). Since the class features are overall stronger, I think it works out okay. Especially because you're expected to have sunk four levels into Fighter or Barbarian or something.

The basic idea of the class is that it transitions you from being a fighter-type to being something more caster-ish. Your spheres give you level-appropriate abilities, and you get casting that's hopefully good enough to fill in some gaps. You also get a full Dragon-equivalent chassis, which might be a bit much. It's possible the class should get knocked down somewhere (probably d10 Hit Die and bad Reflex saves).

There are a variety of different entry paths available. Straight martial is obviously the default, but you can also get in with Gish builds (the pre-reqs are specifically designed to work with Battle Sorcerer, because Battle Sorcerer deserves a leg up). The one thing I'm not sure about is the fact that you can get in as a Sorcerer 8 or similar if you can swing a martial weapon proficiency. Hopefully the fact that doing so delays your progression by a lot mitigates that.

Tartarian Keeper
What is locked must remain locked. What is sealed must remain sealed. What is bound must remain bound.

Sometimes, what has been defeated cannot be killed. Liches whose phylacteries cannot be founded and destroyed, monsters that can only be slain in circumstances not due for millenna, and most famously the titans that birthed the gods. These creatures are bound by chains of steel and magic, trapped beneath the earth or on other worlds. Most would like to forget the things that have been sealed away in such places. But no prison can be left unguarded, and the wardens of such monsters must be formidable in their own right.

BAB: +5
Feat: Combat Reflexes, Improved Trip
Skill: Knowledge (the Planes) 4 ranks
Special: Must be proficient with the spiked chain

Hit Die: d10
Class Skills: The tartarian keeper's class skills (and the key ability for each skill) are Craft (Int), Intimidate (Cha), Knowledge (arcana) (Int), Knowledge (religion) (Int), Knowledge (history) (Int), Knowledge (religion) (Int), Knowledge (the planes) (Int), Listen (Wis), Profession (Wis), Search (Wis), and Spot (Wis).
Skill Points: 4 + Intelligence bonus

1: Tartarian Chain, Improved Reflexes, Tartarian Seal
2: Extended Reach +10, Trip Mastery
3: The Bigger They Are, Warden's Accomodations
4: Extended Reach +20, Dimensional Anchor
5: Tangling Chains, Plane Shift
6: Extended Reach +30, Aura of Chains
7: Lockdown, Whispers of the Inmates
8: Graps of Chains +40, Strangling Chains
9: Opportunist, Animate Chains
10: Extended Reach +50, Imprison

Weapon and Armor Proficiency: The tartarian keeper gains no proficiency with any weapon or armor.

Tartarian Chain: The tartarian keeper gains the ability to call forth the binding chains of tartarus as a weapon. This is a ghost touch spiked chain made of thinaun with an enhancement bonus equal to one half his class level (round up), any any creature tripped by it is entangled (as the spell). Calling it takes one hour. He may only have one such chain at any given time (summoning another destroys any existing one).

Improved Reflexes: The tartarian keeper gains a number of extra attacks of opportunity equal to his class level, beyond those he gains from Combat Reflexes.

Tartarian Seal (Sp): The tartarian keeper can place the seal of tartarus on things. This is like an arcane lock spell, except that knock only bypasses it on a successful opposed caster level check. The keeper is aware when this happens, or if the seal is on is broken, though he does not gain any special awareness of the circumstances in which the seal was bypassed. Caster level equals character level.

Extended Reach: Beginning at 2nd level, the tartarian keeper's finds that he is able to strike foes at a much greater distance. He gains a +10ft bonus to his reach. This bonus increases by 10ft for every two additional levels he gains.

Trip Mastery: At 2nd level, the tartarian keeper adds his class level on checks to trip or resist tripping.

The Bigger They Are: At 3rd level, the tartarian keeper ignores his opponent's size bonus when making a trip attempt.

Warden's Accomodations (Sp): At 3rd level, tartarian keeper gains access to an extradimensional residence. This effect can be used at will, and is like a magnificent mansion, except that the space accessed persists when the duration ends. Creatures or objects left within it will remain there when he returns, though planar travel magic allows them to depart. Caster level equals character level (though the duration applies only to the entrance).

Dimensional Anchor (Su): At 4th level, the tartarian keeper's attacks bind targets to the world. Whenever he successfully trips a creature with his tartarian chain, that creature is effected as by a dimensional anchor. Caster level equals character level.

Tangling Chains (Su): At 5th level, the tartarian keeper can make chains errupt from the ground, binding an enemy to the earth. As a full round action, he can make a melee attack with his tartarian chain against a single target. If the target takes any damage, their movement speed (all modes) drops to 0ft for one round per class level. If they are flying, they fall to the earth. The target can break out of the chains with a strength or Escape Artist check (DC 10 + 1/2 character level + Strength modifier).

Plane Shift (Sp): At 5th level, the tartarian keeper is charged with pursuing escapees across the planes. To facilitate this, he can use plane shift three times per day. Caster level equals character level.

Aura of Chains (Su): At 6th level, the tartarian keeper is surrounded by a field of twisting and grasping chains. This is mechanically equivalent to black tentacles, except that the area an emanation centered on him with a radius equal to twice his reach, the strength score of the chains is equal to his own, and he may have the chains ignore creatures at his option. Caster level equals character level.

Lockdown: At 7th level, any target that takes damage from an attack of opportunity by the tartarian keeper's tartarian chain must make a fortitute save (DC 10 + 1/2 character level + Strength modifier) or be dazed for one round.

Whispers of the Inmates (Sp): At 7th level, the tartarian keeper begins to hear the ramblings of the creatures he is tasked with containing. He can use contact other plane once per day. He automatically makes his save against ability score decrease. Caster level equals character level.

Strangling Chains (Su): At 8th level, when the tartarian keeper uses his Tangling Chains ability, the chains also attempt to suffocate the target. If the target fails a fortitude save, they begin to drown. Breaking out of the chains ends this effect.

Opportunist: At 9th level, the tartarian keeper's reflexes become finely attuned any weakness in his opponents' defenses. Whenever he takes an attack of opportunity, he may take a second attack of opportunity against the same target.

Animate Chains (Sp): At 9th level, the tartarian keeper can bring other chains to life to serve him. He can use animate objects at will, though effect is permanent and the target must be a mass of chains. Animated chains have the constrict ability, a +20ft bonus to their speed, and a climb speed equal to half their speed. He can command 4 HD of animate chains per character level, but chains ordered to guard a specific location do not count against this limit. Caster level equals character level.

Imprison (Su): At 10th level, the tartarian keeper can seal away his enemies alongside his other charges. As a full round action, he can make a melee attack with his tartarian chain against a single target. If the target takes any damage, they are effected as by imprison. They still get a save, and the DC is based on the keeper's strength score.

Spoiler: Author's Notes

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It's a PrC for Tripstars. You get abilities that make you better at tripping and allow tripping to disable high-level movement (e.g. Teleport). Then you gain some utility abilities that hopefully make you slightly more interesting than a normal Tripstar. Not a whole lot to say here. I will say that I'm not satisfied with Animate Chains as an ability. The animated chains it makes aren't very good in combat when you get it, and don't offer any real utility. Also, a lot of the abilities are eyeballed, and I haven't run the math as well as I should on how effective the class actually is at tripping. It's possible one or both of Trip Mastery or The Bigger They Are needs to go.

[Elves]

The dragon one is fairly bland. By contrast, tartarian keeper is very flavorful. I don't like The Bigger They Are -- blanket negation removes depth from tripping and doesn't feel earned. But the class name does evoke the idea of binding giant monsters in chains, which is cool. Perhaps make this a debuff that you have to spend actions to set up?

Grapple seems missing. When you think of binding someone with chains you think grapple first, not trip. There are already a lot of tripper builds; a cool direction for this class would be synergistic tripping and grappling.

For grapples, one thing that springs to mind: magic padlock forms around a target when you successfully grapple them w/ chain, locking them down w/o you having to maintain grapple. That implies being able to make new tartarean chains as like a swift action though.

Too many SLAs imo. Contact other plane should be cut, and if the intent of magnificent mansion is to imprison captured creatures, it could be replaced with an ability specific to that function.

I'd love to see you make more base classes as opposed to PRCs. As you note, the game has been out for 20 years and it may be time to rethink classes from a more basic level. As I've mentioned before I think moving away from daily spell slots is part of this; your shaman for example had more modern gameplay.

[JoshuaZ]

This is a ghost touch spiked chain made of thinaun

Question: If the weapon is then unsummoned, are souls in it released?

[NigelWalmsley]

The dragon one is fairly bland.

Yeah. Dragon flavor has kind of been done to death. The hope is that Spheres setup at least leaves it a little more focused around the abilities Dragons get, though frankly it probably should have just been a dragon-based Conduit riff.

By contrast, tartarian keeper is very flavorful. I don't like The Bigger They Are -- blanket negation removes depth from tripping and doesn't feel earned. But the class name does evoke the idea of binding giant monsters in chains, which is cool. Perhaps make this a debuff that you have to spend actions to set up?

It needs to be a default class feature for tripping to keep working at high levels. High level enemies are Huge or larger, and often have both their BAB and Strength scores higher than a PC can expect at that level. For tripping to keep working, you need bonuses to compensate for or negate those advantages. I could see moving it later or reducing the effect somewhat (e.g. eliminate two size categories difference or whatever), but since the class is pretty much stuck on tripping (or potentially grappling, but that has the same problems), that needs to be at least semi-viable in the overwhelming majority of combats. It's not like a Wizard, where if you face a pile of zombies, you've got Wall of Stone instead of Cloudkill.

Grapple seems missing. When you think of binding someone with chains you think grapple first, not trip. There are already a lot of tripper builds; a cool direction for this class would be synergistic tripping and grappling.

Grappling is out for two reasons. The first is that the class comes to the chains flavor because of the Spiked Chain, which is the signature weapon of trip-based builds. The second is that I just don't want to deal with grappling. The idea is that the various movement restrictions have the fluff you're thinking of.

Too many SLAs imo. Contact other plane should be cut, and if the intent of magnificent mansion is to imprison captured creatures, it could be replaced with an ability specific to that function.

The SLAs, or something like them, is necessary for the class to have things to do outside combat. I'm open to the suggestion that it should have different stuff going on, but any character needs ways to contribute when the combat music isn't playing. Unlike a caster PrC, you can't just smuggle those in by letting it have casting progression.

I'd love to see you make more base classes as opposed to PRCs.

I may at some point. I've got a couple of ideas bouncing around. The problem is that a class is a lot more work to write up. It's twice as many levels to fill, plus a suite of class abilities to pick from, plus possibly archetypes. I have notions bouncing around for some classes (both reworks and new stuff), but when that gets written up is largely up to chance.

Question: If the weapon is then unsummoned, are souls in it released?

Hmm. I actually forgot the details of how Thinaun works when writing that up. The intention is that he gets to capture souls and keep them until released, but that's not how it works at all. I should probably just ditch the special material, and give them an ability that actually does that.

[Elves]

You could let them grapple at range using chains. Deal spiked chain damage instead of unarmed strike damage on success. The "padlock" ability I suggested could help simplify this by replacing the annoyance of checks to maintain a grapple with a flat Escape Artist or Strength DC to escape the Pinned condition.

With a 3-level factotum dip it's still possible to trip big creatures. I would at least push that feature up a few levels if kept.

For utility, like I said it could make sense to replace the mansion with something specifically meant as a place to imprison creatures. If you're removing the thinaun and making it an ability, maybe connect them -- when you capture a soul it goes to your extradimensional prison. Maybe then instead of contact other plane, some ability to forcibly read minds/extract info from your prisoners.

[rel]

I like the tartarian keeper.

I'd remove references to tangling chains coming from the ground so that there can be no argument about whether or not you can bind a flier.

I feel like an explicit synergy between the seal and tangling chain would also help.

An ability to survive in other planes as well as go to them might also be good.

[Magikeeper]

Dragon PRC: Why is this full caster progression? Even without any optimization tricks at all an Elf Wizard/Sorcerer qualifies for this at level 11 for the low cost of some skill points (which they'll make back in 5 4 levels of this class). This gives them 9 levels of d12 hit die, all good saves, +4 con/cha, spell-like abilities, natural armor, etc. Non-elfs can burn a feat for it (again, this is assuming low/no optimization), and probably should. This class benefits spellcasters more than it does martials - in fact, a martial is going to need some optimizing to even benefit from the full casting progression in the first place.

What kind of character is this even for? Gish builds? Gish builds are already near-full casting spellcasters in the first place, they aren't the melee chars that need 5 books and 6 different classes to more-or-less keep up. If someone wants to play a non-gish martial pc, then this class won't help them because if they wanted to be a caster they could just be one!

There's ways to tweak this but.. I think the design philosophy for the first class is pointed towards the wrong direction.

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So, the second class is a lot more interesting, and design-wise it seems to be trying to take an optimized melee build and create a PrC version of it that doesn't require the dumpster diving to set up, and then tossing in a couple utility powers that a normal optimized melee build likely can't get like the mansion / contact plane effect. I'd say more classes in this direction would be the better focus.

-----------------

Also checking out the Mythos classes - https://forums.giantitp.com/showthre...Compendium-2-0 - might be of help since a lot of those were martials intended to be Tier II.

[Morphic tide]

I concur on Dragon Aspirant having way too much casting. If it's to do such a thing as being entry into spellcasting, it ought to either be its own from-scratch progression like Assassin or in the vein of Ur-Priest, or be something like 4-6/10 progression with some variety of "defaulting" to operate like War Mind. Also, that Sphere setup is a really, really borked "light" list thing, since it doesn't layer uses by power at all. You're reasonably getting ahold of at-will Phantasmal Killer and Quickened Fear while also having a Free Action Intimidate, if you double down on Terror, and this is rather at odds with having direct spellcasting progression. On top of that, I don't see any of the options actually being beneficial for a standard Martial character, they're all trying to be a Poor Man's Gish in comparison to the standard options like Abjurant Champion.

I also agree with the notion of graduating the Size Bonus negation on the tripper, and think it's kinda screwy about the order it's giving blatantly-supernatural abilities. Taking existing chains and making them move is one level before the capstone, yet having your own extradimentional house accessed at-will is at level 3, seemingly being readily acquired at ECL 8. And the Extended Reach is way too big for versimilitude on just "has longer reach"; given the other functions of the class, it shouldn't be an issue to tie it to the Tartarian Chain to justify it as having a really long chain. One thought for a larger restructuring would be having the scaling reach instead be a scaling total length of chain, which the abilities alter and make use of in various ways.

It also needs utility abilities (ditto for the Dragon Aspirant). As is, it's going way too far on combat functions, given how it's canning an already core-viable Martial and handing it answers to some of its biggest flaws. Whether that be an edgy Spider Man imitation for mobility, long-distance manipulator applications, more generalized antimagic for various opposing buffstacks and magic-based obstacles, or whatever else, the thing is starting from a virtually optimal battlefield control Martial already, so it can make the extradimensional pocket a major pillar instead of a one-off and focus on versatile options instead of piling on battlefield control.

[Eurus]

Yeah... PrCs that advance full spellcasting are one of the major reasons why martial PrCs seem to suck in comparison. If you want to give it spellcasting, give it its own spellcasting like Suel Arcanamach, that way it's not way better for spellcasters.

[rel]

An elegant way to provide scaling reach and trip based size bonuses is to give the keeper more effective size.
Something like this:

Larger
At first level, whenever it would be advantageous, the keeper is treated as at least size large for the purposes of reach, special size modifiers on opposed checks, whether special attacks like trip can affect an opponent and so on. This doesn't change the keepers actual size or space and never applies in a disadvantageous way.

This power functions as a floor to the keepers size (never smaller than large), but is not an additive bonus. A human keeper with enlarge person cast on them would still only be size large in actuality and effectively, a giant would be actual size huge. In both cases, the characters would get no benefits from this power.

at every odd level after the first, the effective minimum size of Larger increases first to huge at lvl 3, then gargantuan at level 5 and finally to colossal at level 7.

You can tweak the time when it appears, increase levels and wording obviously.
This grants scaling reach, scaling bonuses, and a scaling ability to affect larger creatures.
As an added benefit, it removes the mechanical advantage of the tripper becoming very large.