Winter is Coming (asoiaf)

After an absurdly unlucky death by a stray bullet, teenager Adam Smith is reincarnated at the absolute bottom of the food chain: a tiny snake hatchling in a monster-infested dungeon. Cursed with his trademark misfortune but blessed with an unshakably optimistic spirit, Adam must navigate a world where his own siblings are his first predators. Armed with a new Evolution System that rewards him for every creature he consumes or defeats, Adam begins his grueling climb from a helpless morsel to a cunning hunter. Using his human wit and gradually evolving serpentine abilities, he turns the dungeon's dangers into opportunities.