Tarshak was a DactylDragonkin who was chasing V through many worlds, aiming to kill him. During Hero's Welcome, he is somehow captured by the Necrosyrtes, led by Sakirth. After having V's power transferred into him by Sakirth with assistance of the Elder Mirror, he continually mutates and attempts to take charge of the Dragonkin race.
He is fought twice by the player after the Dactyl Phalaks shoots him with a poisoned dragonbane dart, and after being defeated, flees to Brimhaven Dungeon where he mutates even further and becomes an Abomination. It manages to survive the player's attempt to crush it with bane ore in the sanctum, but the player eventually kills it in combat.