Imp is a very small, red devil-reaper mouse with black wings, little horns, and inside ears. He has a silver-white mask-shaped marking over his eyes and a bony tail. When he becomes angry, as shown in episode eight, the whites of his eyes become black, his pupils turn yellow, he starts to drool black liquid, and his teeth and horns are pointier. In the finale, when he escapes from the pocketwatch imprisonment, he becomes a cat reaper of unknown breed. His bony tail becomes normal, his wings and horns disappear, his eyes become permanently yellow, and he goes back to his normal size, slightly larger than May .
Imp was banished from the Rift into a golden pocketwatch. He later meets May , and then crafts a deal with her in order to escape his banishment.