He is a short Domani who is graying at the temples.
Mezar bonded Adrielle unwillingly, although they have now become fond of each other. He has Traveled to Tear to join up with Logain and Rand. He watches Rand's meeting with the Daughter of the Nine Moons from a distance and Travels in as backup when it is revealed that the Daughter of the Nine Moons is actually Semirhage.
Mezar suddenly turns up at the Black Tower and becomes one of Mazrim Taim's favorites. His eyes also change, looking different, and his smile is wrong according to Norley. Most likely, he was turned to the Dark One by a circle of thirteen Myrddraal and thirteen Dreadlords.