Abrim was the Grand Visier to the Seriph of Al Khali of Creosote of Klatch. In Sourcery, he captures Rincewind and Conina and takes the Archchancellor's Hat from them and, by wearing it, becomes its vessel since he has enough magical power for the hat to use him for its purposes. As Grand Vizier he is a manipulator and the true eminence grease behind the throne.
Abrim explains to Rincewind that he had magical potential and had applied to the university but was considered too mentally unbalanced for admission. This surprised Rincewind, since he was more than aware that the mental stability of most wizards could be described on a scale with the labels: 'Insane' and 'Insane beyond belief'. So to have an insane Vizier pseudo-wizard being controlled by a hat running amok inevitably leads to a reigniting of the Sourcerer Wars. Abrim builds a Tower of Magic in Klatch to fight those mages at Unseen University. He is distracted by The Luggage and is killed by an attack from Marmaric Carding during Rincewind's attempt to stop the war.
His name connotes 'abrim' meaning full to the very top - in his case, full of insanity, magic, sourcery, power, etc.
- Sourcery(First appearance)