The Djinn Garden
by Stephen Goldin
In a world of Arabian Nights adventure, a band of heroes is on a quest to reunite the Crystal of Oromasd and save the world. One of their number, the beautiful young djinn named Cari, vanishes on a mysterious island in the Central Sea and the others must avoid being enslaved themselves and defeat a powerful invisible demon if they hope to rescue her.
(This is a story from The Parsina Saga.)