Making Castlevania's Soma Cruz in D&D

[Nettlekid]

I've always had a soft spot for "I defeat you and gain your power" type characters. From the aforementioned Soma Cruz of Castlevania's Aria of Sorrow and Dawn of Sorrow to Kirby, to

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That chef guy who ate animal organs and gained animal powers, not to mention

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Cas who just cut open an angel's throat and ate that angel's grace

, that kind of character who purposefully hunts down strong opponents to become ever stronger themselves is just so cool. Is there any kind of structure in place that allows a character in D&D to do that?

I'm thinking PrCs mainly, but I'm open to other suggestions. Both Necrocarnate and Soul Eater fit very thematically and involve strengthening themselves by killing, but the benefits are too generic and too temporary. They don't have much to do with the actual power of the defeated enemy, and they need refueling. I guess I'm after a more generic and far less broken version of Illithid Savant, because that "brain eating, ability harnessing" thing is just what I'm after.

[Vincent Dragon]

Greater Doppelganger and Neh-Thalggu can do similar.

The first ate brains to copy not just the form of someone, but its memories and abilities.

The second swallow brains by teleporting them (!!!) directly into its "stomachs" and then gains Sorcerer spellcasting levels for that (can eat up to 13 brains).

Probably there's more than that, but it's what i remember right now.