Fire Imp

The Fire Imp is a Caster enemy found only in the The Underworld. It shoots a volley of Burning Spheres which go through tiles, but can be halted by the swing of a weapon. These spheres can inflict the On Fire! debuff if they land.

The Fire Imp will pause for a few seconds after firing 3 times, offering a good opportunity for attack, then teleport to another location nearby. It will also pause if it gets hit. It will follow you by teleporting if you try to flee (unless you teleport away with a Magic Mirror, reach a depth of 0ft, or die).

Trivia
Diablotin de feu Fire Imp Fire Imp Огненный черт
 * The fact that it drops a Plumber's Hat might be a reference to Super Mario Bros., as Mario could shoot fireballs.