Mezaryl is a one-eyed weapon dealer located in the Marketplace of Blade Square in Trithik.

She is a very useful NPC:

Mezaryl is also involved in several quests and rewards. (Hidden for spoiler potential)

Spoiler Information
She sells one of the gems for Tzal-Toalth, for 16 AT (or 8 AT with Diplomacy of 70)
Spoiler Information
You can swap her your weapon from Iakor for a new weapon (Shimmering Silver Sword, Axe, etc.) that will change your alignment to Saintly. This was originally a function of her store in the Festival of Blades.
Spoiler Information
After you complete the 7 Goblins final quest, "The Altar of Malice", she will be able to swap the special MR bonus to another weapon, and the SP bonus to another armour, for a cost of 1000 gold. You can swap the bonus as many times you want, as long as your gold holds out.

Historic Note: Initially the price was 5000, but at some (unknown) point in time it was reduced to 1000