Yuan-ti pureblood from MotM. 1-3 levels in Divine Soul Sorcerer, 3 levels in Fathomless Warlock, pact of the chain w/ pseudodragon familiar. Fathomless warlock's tentacle reflavored as a hydra head, arms of hadar being hydra heads, pseudodragon reskinned as a miniature hydra - favored by the gods and divine soul healing spells could be the character regenerating themselves from grievous wounds. Conceptually, the fathomless warlock levels are the character's ancestral powers coming out stunted and hard to control (as pact magic is always upcasted) - flavor wise, it's like a sorcerer without a good control of their stronger magic.

The backstory; This character's grandmother was Lernaea, the hydra goddess that was slain by Tiamat. Parent could be a really advanced spellcaster that somehow entertained a relationship with a demigod hydra who was the daughter of Lernaea (when magic is involved anything is possible) - of course under the lore assumption that "demigods" aren't just lesser gods but also the offspring of the gods in the form of very powerful/mythical monsters (like Poseidon was infamous for) - as such, they aren't the only demigod in their family tree. Their brother is a full fledged hydra that destroyed her hometown, including her mortal parent, because he's pissed about being related to a humanoid. Character swears revenge against her patricidal brother. Maybe some story beats where killing this hydra lets her claim the vestiges of her brother's divine spark and get a stronger connection to her ancestry? I don't know, but I've been hooked on this character idea since I've thought of it. Maybe the pseudodragon familiar could be a a vestige of the grandmother hydra's spirit manifesting.

Thoughts? How would you build this?