Rellor is a new Pokémon for Pokémon Scarlet and Violet, and it has special requirements to evolve it into its final form, Rabsca.
Just like Pawmot does upon evolution, Rabsca learns the move Revival Blessing, which revives one of your fainted party members. This is an extremely useful move, making this bug- and psychic-type Pokémon is a good addition to any well-rounded party.
To evolve Rellor, you’ll have to walk around with it.
Where to find Rellor
Rellor can be found in the desert in western Paldea. It’s a pretty small Pokémon, so you’ll have to look for it carefully.
How to evolve Rellor in Rabsca
To evolve your Rellor into Rabsca, you have to walk with it in Let’s Go mode — when you release a Pokémon from its Poké Ball by pressing the R button. After taking 1,000 steps, your Rellor will evolve into Rabsca the next time it levels. (You can level it by making it gain EXP via battle or by using a Rare Candy.)
We didn’t see any type of pedometer or other step counter in the game, so the best thing to do is to just walk around with Rellor for a while and then level it up after a bit. If it doesn’t evolve, you just need to walk with it more.
If you run too fast, Rellor will return to its ball, so we just leisurely snuck around while crouching (press B to crouch and sneak) around Mesagoza.