Jailer

Jailers are a race of demons in service of the Burning Legion that carry fel cages on their backs. As their name suggests, they act as jailers and caretakers of the Legion's prisoners and use their cages to capture both the soul and body of their enemy, which they then send to the Twisting Nether to subject their victims to horrific torture and interrogation.

History
In Year 26, an inquisitor described the jailers as a "new type of demon".

Traveler
At least two jailers served Highlord Xaraax in the Hidden citadel in the Hellfire Peninsula some time after the Cataclysm on Azeroth. One began to siphon Greydon Thorne in order to empower the Darkstorm when Makasa Flintwill led her army against the stronghold. He was quickly killed by Murky who threw his spear, hitting the demon's head. The second one brought several chained Gordunni ogres and red imps to Malus who sacrificed them to the Darkstorm.

Third invasion
A vast number of jailers participated in the third invasion of Azeroth.

They were also encountered on Niskara, Shadowgore Citadel, Dreadscar Rift, Argus, and the Invasion Points.