Xanthor
Archmage of Erathia under Catherine.
He is also the narrator (along with Marcus Finch) in a few of the short stories that NWC employees had published on the now-defunct "The Nether Gods" fan site. According to these stories, he is the nephew of Agar.
In Horn of the Abyss , he was captured and imprisoned by the barbarians and eventually rescued by Bidley. In gratitude for being saved, he told Bidley the location of Island of the Vengeful Serpent - the resting place of the Horn of the Abyss.