Sorceress of Darshiva  cover illustration by Geoff Taylor

Sorceress of Darshiva by David Eddings
The fourth book in the Malloreon series 1989
Garion and his companions continue their desperate search for Zandramas, the Child of Dark and abductor of Garion's baby son, Geran. Led by the orb from Mallorea to the island of Melcena, they discover the place the sardion once rested and also find Senji, a wizard.