Honorius — A ninth-level afrit, invulnerable to the magic of mere djinn, whose essence occupied the skeletal remains of the late William Gladstone and relentlessly guarded Gladstone's buried treasures. He went mad after one hundred years of such confinement.
Horla — A subclass of djinni appearing as shadowy apparitions to humans, causing madness and disease.
Humbaba — In Accadian mythology, Humbaba was a monstrous giant and guardian to the Forest of Cedars. Under the orders of a former master, Bartimaeus distracted the dim-witted giant and slew him.
Ianna — A djinni who had long been an ally to Asmoral, a fellow djinni who perished rather than bring about Ianna's demise.
Imp — A manipulative form of spirit lower in rank than marids, afrits, djinn, and foliots.
Jabor — A powerful djinni with a voracious appetite; enslaved by Simon Lovelace. In Ancient Egypt, he served Anubis, the god of the dead.
Marid — The most powerful rank of demon normally called to work under a magician's service. They radiate so much power that it's possible to track their movements by following a residual magical trail.
Median Magi — A priestly tribe of ancient Persia, whose fabled power over demons gave rise to the term magic.
Messenger Imp — A minor demon charged with carrying messages to magicians; usually after breakfast and shortly before sundown.
Mite — The lowest form of demon, possessing very little intelligence.
Mouler — A lowly form of demon.