Jammomancer

Jammomancers are rare variants of Gunsingers. They stand still and jam one enemy in the room. Jammed enemies deal 1 full heart of damage, move and shoot faster, deal contact damage if they didn't already, and have triple their normal health.

If the player gets near or attacks a Jammomancer, it will run away and its buff will be interrupted.

If the Jammomancer is the only enemy left in the room, it will immediately charge at the player.

Jamerlengo
Jamerlengos behave similarly to Jammomancers, but are able to simultaneously jam every other enemy in the room. Unlike Jammomancers, Jamerlengos will pause for a little bit before charging at the player if they are the only enemy left in the room.

Trivia

 * The Jamerlengo's name is a pun on "Camerlengo", an office of the Roman Catholic Church.
 * Jammomancers will immediately charge at the player when they're the last enemy left, unlike Gunsingers, Ammomancers, and Jamerlengos, who stand in place beforehand.
 * Jammomancers appear to wear mitre hats with crosshairs on them, similar to Cardinals, while Jamerlengos seem to wear shotgun shell-shaped hats.
 * Prior to Advanced Gungeons and Draguns, the Jamerlengo was the largest enemy that could be pushed into a pit, now second to the Tarnisher.