Abishai

Abishai (used both as singular and plural) or abishais, also known as scaly devils, were a type of devil in service to the Queen of Chromatic Dragons, Tiamat. The draconic devils were, among many other roles, the guards and escorts of the the Nine Hells' captives, processing them for torture when not corrupting mortals themselves.
Unlike most devils, abishai seem to exist outside of the traditional hierarchy, acting at times as Tiamat's servants and jailers.