Queezle was a female djinni with whom Bartimaeus is known to have had a deep relationship. She has done time in Asia, and was working with Bartimaeus at the fall of the Holy Roman Empire. She was later reunited with Bartimaeus during the Golem Affair, but unfortunately she was later killed (maybe) by the Golem itself.
Queezle's first summoning occurred only 1500 years ago, her master being a hermit in the Jordanian desert who treated Queezle not with the usual harshness of a master-slave relationship, but with austere coutesy. After he died, she remained in the Other Place until a French magician woman summoned her in the 1400s; this master was also not as cruel as most.
She served alongside Bartimaeus in the battle in Prague, where the British Gladstone overran the Czechs and defeated them; fortunately for the two spirits, their master was killed before they were harmed in the fighting, allowing them to be released to the Other Place. Since then, she served in China and Ceylon until summoned by a magician by the name of Ffoukes in Britain. He assigned her to surveillance duty during the Golem affair, which incidentally happened to be the same task Bartimaeus had been assigned to, allowing them to work together once more.
She was killed by the Golem during routine surveillance duty on a rainy night; she and Bartimaeus had just switched surveillance routes, leaving her located at a crossroads to seven roads, sitting on the plinth underneath a statue of a man on rearing horse. Bartimaeus had traveled just two blocks away from said location when she sent up a flare; when he got there neither Queezle nor her assailant were anywhere to be seen. It is implied that she was killed by one of the Golem's magical energy blasts.
Thanks to her luck with kind (or at the very least not overtly cruel) masters, Queezle's personality was less cynical and bitter than most spirits'. She maintained good humor in tense situations and was not afraid to take on dangerous tasks.