As a zulkir, Baltreyo was a member of the ruling council of Thay. He was also a strong ally of Valindra Shadowmantle.
Baltreyo was gifted with the ability to adopt illusory forms in order to battle with different abilities. These forms were based on people his foes knew.
During the assault on the Dread Ring, Sergeant Knox learned from Rath Modar the identity and whereabouts of Baltreyo. To disrupt Valindra Shadowmantle's schemes, he sent an adventurer on a quest to go through a portal to the City of Thay and slay Baltreyo. Under cover of night, the adventurer invaded the Phantasmal Fortress and made their way past the zulkir's minions to battle Baltreyo and attempt to destroy his phylactery.