This is a character I've had in my brain for YEARS and never did much with. I always wanted to do more with him, maybe feature him as a deuteragonist in a story about adventure and self discovery?

His thing is that he can absorb matter and convert it into fat, muscle, and bone mass. but mostly fat. These items are not lost however, as his ability consists of 3 parts:

1: the breaking down of anything that passes through the skin on his gut
2: an exact, 100% accurate model down to the molecular level of any item absorbed being stored in his brain immediately upon it's complete absorption
3: the ability to construct anything using his stored up potential, provided he has stored the requisite materials

in this way, not only can he functionally "store" anything inside his body and retrieve it at will, provided his belly is accessible, but he can also absorb things and create NEW things from them. so for instance, if you lobbed some iron bars, some wood, and some leather at his belly, he's be able to shake his gut around a bit (mostly for dramatic effect) and pull out a sword, provided he's studied the layout of swords.

Unfortunately though, the imprints in his brain are not permanent. If he ever absorbs something, and then uses up the prerequisite materials, he loses that imprint. So those iron bars are no longer stored in his memory once the sword is made. this is also why he eagerly absorbs basically everything he can get his hands on, because he wants to study them and commit their imprints to his actual memory rather than just the temporary spell slots in his brain. He carries around a huge book of knowledge he's gained about the molecular structure of different objects, and his ability to produce things is so accurate he can even do something like produce a sword that's already been tempered to be harder, or bombs with chemical reactions that are ABOUT to go off but havent yet

This does infact also mean that he can absorb PEOPLE and then bring them back out, but he only does so to people he wouldn't mind actually dieing, because effectively they DO die when he does this. their bodies are atomized and spread across his form, their life essence stored as naught more than an unconscious "spark" inside him, which can be used to push them back out alive, yes, but should he ever accidentally or forgetfully use up the parts that the person was made of, that person is lost forever, their soul merely a blank conciousness stored in his fat that can, if he so desires, be used later.

So, yes, at higher levels he is capable of droning people if you're into that. or transforming people into living objects TF style, though it's a bit more... clean body horror than "awww what a cutey i'm gonna make you into a speedo and wear you to the pool" or something.