Evolving Hisuian Qwilfish into Overqwil in the Indigo Disk DLC for Pokémon Scarlet and Violet is a bit different from how it was in the game the creature originally debuted in, Pokémon Legends: Arceus. Hisuian Qwilfish is the regional variant of the Generation 2 Pokémon, though instead of being a Water- and Poison-type monster like its original Johtonian form, it embraces a Dark- and Poison-type combination. It also takes on a slightly different design, with a darker color palette and angrier looks.
https://screenrant.com/pokemon-indigo-disk-dlc-evolve-hisuian-qwilfish-overqwil/