Athrak was the leader of a colony of magpies, who followed orders from Queen Silth. He and the rest of his colony guarded the sky, so that nobody could escape or enter Marlfox Island without being seen. Silth also used them to keep her army of water rats in check. Any rat who displeased the Queen would be captured by the magpies, and possibly dragged to the Teeth of the Deeps, as Rigglent found out to his cost.
Athrak's colony attacked any creature who approached or landed on the island. They once wounded a kingfisher, who managed to escape and give information about Marlfox Island to Ellayo Swifteye. Later, they attacked the osprey Megraw while he was asleep, dislocating his wing, but unwittingly creating their own worst enemy in doing so. After his wing was healed, a vengeful Megraw returned to slay Athrak and his entire colony.