(This is just to explain his power)

Hybridization

It is a innate skill which allows him to change his form by replacing and adding bodyparts with non human parts, the ammount of mutations he can have active at any time is equal to 2 + his level, to change a mutation, it takes a minute to change a mutation, he can't deactivate the mutations, with levels he will gain the ability to change his own body in things such as size, hair color and such

For exampme

Claws

He may integrate claws onto his body from some kind of none monster animal. the animal for balance reasons will be "random" (dont want to make him op with the arm of mantis shrimp or something)(prob just go for a cat or something)

I also to make them longer and sharper based on certian stats eg stregth for length and dexterity for shapness or something

Additionally, I'm doing a rule where after killing 1000 of the monsters, I will roll a dice, on a 6 he will gain a random a monster part (drop item) to his register from the monsters he killed, ill spin a wheel for it.

Obviously it would be broken if he had like wings at level one, so I will be using unlock levels such as

-claws at level 1

-whiskers at level 2

-tentecules at level 3

-venom sac at level 4

-wings at level 5

The more complex something is, the higher the level required is