Agachak was the Grolim Hierarch of Cthol Murgos, specifically of Rak Urga. He was a cadaverous man who enjoyed games of power and manipulation. He wore a blood-red hooded robe and had a long beard, sunken eyes, and shaggy gray brows. He had a hollow voice.
Thinking they were Nyissan slavers, he inadvertently captured Belgarion and his companions as they pursued Zandramas. His goal was to use them to help smuggle the Dagashi Kabach (really the Grolim Harakan) behind Mallorean lines to execute Zakath. Agachak was playing a game of power with his mistress Chabat, whom he knew was trying to raise a demon to overthrow him, but he let her believe he was unaware of this.