I read this book in the early 2000's, and believe it was published in the late 1990's. The story was told from the points of view of several main characters, and the author made mention of experimenting with this form in the jacket cover.
The main plot centers around a great general or warlord (I think "warlord" was part of the title, but I can't be sure). The warlord was in fact the spirit of a long-dead conqueror who had been renowned as a military genius, inhabiting the body of one of the mages who was struggling to control him. The mages were the ruling class, with the high-mage essentially being the king and the mage college having a very high position in the society.
Two of the other key characters are a barbarian who is captured and made the slave of the high-mage's daughter and the daughter herself who is attending the mage college.
Part of the plot climax concerns the mage who was holding the warlord's spirit in his body losing control and becoming fully possessed by the warlord.