Unless you are a fan of bugs in real life, you likely will not be too drawn to a Pokémon like Rellor. This Pokémon seems to be an obvious creature inspired by the real-world dung beetle, which is not quite endearing to most people. That being said, if you want to fill out your Pokédex, you will want to add it to your list of captured Pokémon and then evolve it. Here is how to evolve Rellor into Rabsca in Pokémon Scarlet and Violet.
How to get Rellor to evolve into Rabsca in Pokémon Scarlet and Violet
After you have caught Rellor in Pokémon Scarlet and Violet, you can get it to evolve into Rabsca at any point you want afterward, but it will take a bit of traveling. This Pokémon does not evolve from leveling it up or giving it a certain item. Instead, you need to move it to the lead of your Pokémon party and then let it outside by pressing ZR. You then need to let it follow you for 1,000 steps.
From what we have seen, the 1,000 steps you take with Rellor following you need to be done in a single patch of travel, so make sure you do not outrun it or battle any wild Pokémon. With this in mind, we recommend finding an open spot in a city, throwing it out, and then running in circles for a while. This could turn into a method that feels like it takes forever, so we recommend doing this while listening to a podcast or some music to pass the time. When you think you have passed the 1,000-step mark, give it a Rare Candy, or have it level up once by battling, and it will evolve into Rabsca.
When your Rellor becomes Rabsca, it will adopt the Psychic-type to go with its already present Bug. This leaves it weak to a lot of attacks, including Bug, Dark, Flying, Fire, Ghost, and Rock attacks. It will be resistant to Fighting, Grass, Ground, and Psychic moves.