However, it turns out this is rather a complex endeavor - long story short, I have no fucking idea if this is really balanced or people would want to play it. Hopefully you do, and you can pause between insults long enough to give some useful feedback on that point.
I think this probably could go up to 20th level, but for now I'm focusing on the first 10. While I'd like this to work with multiclassing, that's not my primary concern - go ahead and mention anything broken though. Also, I feel like the ability lists might be a little sparse right now, so if you have more ideals for inclusions then post them. Without further delay:
Shapeshifter
"Quote goes here"
A Shapeshifter is a master of forms, able to assume almost any shape. Unlike spells such as polymorph, the Shapeshifter is not limited to the forms and abilities of existing creatures, although they can choose to mimic them. Also, they can pull off T-1000/Venom style shit while their stamina lasts.
Hit Die: d12
Class Skills: Acrobatics, Bluff, Climb, Disguise, Escape Artist, Fly, Intimidate, Knowledge (local, nature, planes), Perception, Stealth, Survival, Swim
Skill Points/Level: 4 + Int
BAB: Medium, Saves: Good Fort and Reflex
Level, Abilities:
1 Shapeshifting, Physical Improvement, Basic Abilities
2 Shift Size, Morph Initiate
3 Extended Shapeshifting, Item Bond
4 Quick Shifting, Physical Improvement
5 Shift Size, Expert Abilities
6 Morph Adept
7 Diverse Shapeshifting, Physical Improvement, Item Hoarder
8 Instant Shifting, Shift Size, Advanced Abilities
9 Morph Master
10 Limitless Shapeshifting, Physical Improvement, Master Abilities
Shapeshifting: As a standard action, the Shapeshifter can change shape to any humanoid form. When doing so, it can select the effect of any Shifting abilities it has available. Gear that no longer fits merges into its body and becomes inert. The Shapeshifter gains a +10 bonus to Disguise to resemble the new form.
Physical Improvement: When changing form, the Shapeshifter gains a +4 bonus, divided as they wish among their physical ability scores. This improves by +2 at 4th, 7th, and 10th level.
Basic Abilities: When changing form, the Shapeshifter can select three abilities, plus one for every three levels. Abilities cannot be selected twice unless stated otherwise.
* Gain a natural attack (bite, claws, tail slap, wings, etc). This does standard damage for your size.
* Trip or Grab, as the monster ability, on natural attacks
* Grow quills which can be shot as a ranged attack, increment 40', standard claw damage.
* +2 natural armor
* resistance 5 to one type of energy
* +8 to Escape Artist.
* Endure elements, as the spell
* +10' to movement speed, +2 to Acrobatics
* swim 20', and water breathing
* climb 20', +8 to Climb
* darkvision 60', low-light vision, or scent
* Gain a bonus equal to your level to Stealth checks
* Gain a bonus of twice your level to Stealth checks when standing still
* Trip or Grab, as the monster ability, on natural attacks
* Grow quills which can be shot as a ranged attack, increment 40', standard claw damage.
* +2 natural armor
* resistance 5 to one type of energy
* +8 to Escape Artist.
* Endure elements, as the spell
* +10' to movement speed, +2 to Acrobatics
* swim 20', and water breathing
* climb 20', +8 to Climb
* darkvision 60', low-light vision, or scent
* Gain a bonus equal to your level to Stealth checks
* Gain a bonus of twice your level to Stealth checks when standing still
Morph Initiate: At 2nd level, the Shapeshifter learns to harness their shifting ability to produce more sudden and potent changes than normally possible. This does, however, consume more stamina. The Shapeshifter gains a Stamina pool equal to half their level + their Con bonus. The pool refills with five minutes of rest. When out of Stamina, the Shapeshifter can still use Morph abilities, but takes a point of Con damage each time. Morph abilities are a free action and can only be used once a round unless stated otherwise.
* Gain an Ability for one round.
* Triple your reach for one attack.
* Take an extra move action.
* Fortify yourself against an attack, reducing damage by [Level + Con bonus]. Immediate action.
* Wrap around an enemy that hits you, initiating a grapple. Immediate action.
* Heal damage equal to [Level + Con bonus]. Standard action.
* Triple your reach for one attack.
* Take an extra move action.
* Fortify yourself against an attack, reducing damage by [Level + Con bonus]. Immediate action.
* Wrap around an enemy that hits you, initiating a grapple. Immediate action.
* Heal damage equal to [Level + Con bonus]. Standard action.
Item Bond: At 3rd level, the Shapeshifter can benefit from the magic properties of one item that's melded into their form. This is in addition to anything they can wear, but it still takes up the slot.
Quick Shifting: At 4th level, the Shapeshifter can change shape as a move action.
Expert Abilities: At 5th level, the Shapeshifter can grow better abilities.
* Gain two natural attacks. Replaces the basic ability.
* Gain injury poison on your natural weapons. Stats: 1d3 to one physical, duration 6 rounds, one save.
* Spit contact poison, range 30'. Same stats as above.
* Gain a rake attack.
* Gain a grab and constrict attack.
* Gain a bite with a blood drain attack when grappling; it deals 1 point of Con damage, you heal 5 hp.
* Extend your reach by 5' (10 if Huge+).
* Gain a stench aura; 20' radius, sickens, immune after successful save.
* +4 natural armor
* fast healing 2
* DR 5 / slashing, piercing, or bludgeoning (choose one).
* +20' to movement speed, +8 to Acrobatics
* swim 40', and water breathing.
* climb 40', +8 to Climb
* fly 40' (average)
* burrow 30'
* blindsense 30'
* darkvision 90', or superior low-light vision
* Gain injury poison on your natural weapons. Stats: 1d3 to one physical, duration 6 rounds, one save.
* Spit contact poison, range 30'. Same stats as above.
* Gain a rake attack.
* Gain a grab and constrict attack.
* Gain a bite with a blood drain attack when grappling; it deals 1 point of Con damage, you heal 5 hp.
* Extend your reach by 5' (10 if Huge+).
* Gain a stench aura; 20' radius, sickens, immune after successful save.
* +4 natural armor
* fast healing 2
* DR 5 / slashing, piercing, or bludgeoning (choose one).
* +20' to movement speed, +8 to Acrobatics
* swim 40', and water breathing.
* climb 40', +8 to Climb
* fly 40' (average)
* burrow 30'
* blindsense 30'
* darkvision 90', or superior low-light vision
* Engulf a foe you successfully grapple. They are pinned, cannot see or breathe, and you block line of effect to/from them. The engulfment lasts until you release them, but if they break the grapple they can attack you from inside (you are Dex 0 against this).
* Take an extra attack action.
* Squeeze yourself through a gap of any size.
* Negate a critical hit or precision damage. Immediate action.
* Spit acid, dealing 1d6/level in a 30' cone or 60' line. Attack action.
* Escape any binding or grapple.
* Take an extra attack action.
* Squeeze yourself through a gap of any size.
* Negate a critical hit or precision damage. Immediate action.
* Spit acid, dealing 1d6/level in a 30' cone or 60' line. Attack action.
* Escape any binding or grapple.
Item Hoarder: At 7th level, the Shapeshifter can use any number of items (subject to the normal slot limits) that are melded into their form. In fact, they can have a bunch of items melded, as many as would fit in a Bag of Holding, and switch between them whenever they shapeshift.
Instant Shifting: At 8th level, once per round, the Shapeshifter can change shape as a free action.
Advanced Abilities: At 8th level, the Shapeshifter can grow even better abilities:
* Pounce
* Gain a rend attack
* Gain a trample attack
* Gain a tongue attack. It does not damage but has triple reach and the Grab ability.
* Gain a swallow whole attack, as the monster ability.
* Grow an extra pair of arms.
* Gain a web attack, as the monster ability.
* Be covered in contact poison, same stats as the Expert ability.
* +6 natural armor
* regeneration 5 (disintegration) or fast healing 5.
* resistance 10 to two energy types.
* DR 5/adamantine
* No need to breathe, and endure elements (as the spell)
* +30' to movement speed, +8 to Acrobatics, triple jumping distance
* swim 90', and water breathing
* spider-climb 60'
* fly 60' (good)
* blindsense 60', or blindsight 30'
* Gain a rend attack
* Gain a trample attack
* Gain a tongue attack. It does not damage but has triple reach and the Grab ability.
* Gain a swallow whole attack, as the monster ability.
* Grow an extra pair of arms.
* Gain a web attack, as the monster ability.
* Be covered in contact poison, same stats as the Expert ability.
* +6 natural armor
* regeneration 5 (disintegration) or fast healing 5.
* resistance 10 to two energy types.
* DR 5/adamantine
* No need to breathe, and endure elements (as the spell)
* +30' to movement speed, +8 to Acrobatics, triple jumping distance
* swim 90', and water breathing
* spider-climb 60'
* fly 60' (good)
* blindsense 60', or blindsight 30'
* Shapeshift as an immediate action.
* Bud off a duplicate. It has your stats, 1/4 your hp, but can only take move actions. It lasts for one minute.
* Instead of dying, drop to -10 (if not already lower) and enter suspended animation until you reach positive hp.
* Go into stasis for one round, becoming immune to anything that only works on living creatures. Standard action.
* Meld with a living creature at least one size larger than you. It doesn't detect your presence (unless it saw you do this). You cannot take actions while melded, but can see through the creature's senses. You can break the meld as a free action, shifting into an adjacent square. If the creature knows of your presence, it can try to evict you with a Fortitude save, once per hour.
* Assimilate a living creature. Make a touch attack. If it succeeds, the creature takes 1d6/level damage and must make a Fortitude save. If they fail, they are absorbed completely by you. They cannot be resurrected, but a Wish can release them (or you can choose to do so). You gain +10 to Disguise to impersonate the absorbed creature.
* Bud off a duplicate. It has your stats, 1/4 your hp, but can only take move actions. It lasts for one minute.
* Instead of dying, drop to -10 (if not already lower) and enter suspended animation until you reach positive hp.
* Go into stasis for one round, becoming immune to anything that only works on living creatures. Standard action.
* Meld with a living creature at least one size larger than you. It doesn't detect your presence (unless it saw you do this). You cannot take actions while melded, but can see through the creature's senses. You can break the meld as a free action, shifting into an adjacent square. If the creature knows of your presence, it can try to evict you with a Fortitude save, once per hour.
* Assimilate a living creature. Make a touch attack. If it succeeds, the creature takes 1d6/level damage and must make a Fortitude save. If they fail, they are absorbed completely by you. They cannot be resurrected, but a Wish can release them (or you can choose to do so). You gain +10 to Disguise to impersonate the absorbed creature.
Master Abilities: At 10th level, the Shapeshifter can grow truly excellent abilities:
* Gain four natural attacks. Replaces the Expert ability.
* Gain injury poison on your natural weapons. Stats: paralysis 1 round, duration 6 rounds, one save.
* Gain injury poison on your natural weapons. Stats: 1d4 to one physical, duration 6 rounds, two saves. Replaces expert ability.
* Spit contact poison, same stats. Replaces expert ability.
* Grow three extra pairs of arms.
* Gain rock throwing and rock catching, as the monster abilities.
* resistance 20 to two energy types.
* hardness 5
* +60' to movement speed, no terrain penalties, +8 to Acrobatics, triple jumping distance
* fly 90' (good)
* burrow 60' and tremorsense 90'
* blindsight 60'
* Gain injury poison on your natural weapons. Stats: paralysis 1 round, duration 6 rounds, one save.
* Gain injury poison on your natural weapons. Stats: 1d4 to one physical, duration 6 rounds, two saves. Replaces expert ability.
* Spit contact poison, same stats. Replaces expert ability.
* Grow three extra pairs of arms.
* Gain rock throwing and rock catching, as the monster abilities.
* resistance 20 to two energy types.
* hardness 5
* +60' to movement speed, no terrain penalties, +8 to Acrobatics, triple jumping distance
* fly 90' (good)
* burrow 60' and tremorsense 90'
* blindsight 60'