Tanis, The Shadow Years — Barbara Siegel; Scott Siegel

The sixth and final book in the Preludes series follows Tanis Half-Elven on a dangerous adventure through time and memory
 
The tale is told that Tanis Half-Elven once disappeared in the mountains near Solace. He returned changed, ennobled -- and with a secret. No one knew what happened to him in those mist-shrouded peaks. Until now.
 
Accompanied by his new dwarf acquaintance, Clotnik, Tanis chases after information about his mysterious and long-dead father. His search leads him to Kishpa, a dying, lovesick mage who holds the answers to Tanis' burning questions -- but who needs Tanis' help first. So begins a wild adventure in which Tanis becomes a traveler in Kishpa's memory, journeying into the past to fight an impossible battle against time itself.