The Sundered Realm

Description for THE SUNDERED REALM by Robert E Vardeman and Victor Milan:

Fost Longstrider's mission seemed ordinary.  He'd been hired to deliver a jug to a wizard on the far side of the forest.  Unfortunately the jug contained a sex-starved genie, the wizard was dead by foul means, and Fost was probably the next to die.

Then the genie was stolen and spirited away to the City in the Sky.  It was up to Fost to steal it back from two beautiful sisters.  They were fighting to become queen and , using dark powers, one had called forth a demon.  Now Fost's foray was suddenly a terrible war.

This is #1 in War Of Powers Series.