Ammomancer

Ammomancers are enemies that vaguely resemble Gunsingers but paler and wearing darker robes.

If left uninterrupted, Ammomancers will stand still and summon a Shelleton. The summoning can be interrupted by getting close to the Ammomancer or hurting it, causing it to run away, or by killing the Ammomancer.

If left alone in a room without any other enemies or after summoning a total of 3 Shelletons, Ammomancers will go mad, stop their summoning rituals, and instead will attempt to hurt players by running into them.

If an Ammomancer successfully summons a Shelleton but is killed afterwards, then the Shelleton that was summoned will collapse into its skull, allowing the player to finish it off more easily.

Trivia

 * In the Portuguese translation of the game, they are known as "Necropolvorista", a portmanteau of the words "necromante" (necromancer) and "pólvora" (gunpowder).