FusionDex

Deiby rely on thermal radiation to sense other Pokémon around them, as they are completely blind. When encountering a Pokémon that does not release heat, they become aggressive and blindly headbutt everything around them until they calm down.

If a Deiby is spouting yellow flames from its mouth, it is in good health. They cannot see, so they tackle and bite to learn about their surroundings.