The Grolim were the hereditary priesthood of the Angaraks and of their god, Torak. They worshiped him in their temples, making use of bloody sacrifices to please him. They always wore black robes. Some Grolims were sorcerers, and they were distinguished by a lining to their robes. Grolims often wore steel masks.
Grolims were found throughout Angarak lands, but they did not have their own country. In Mallorea, their power was balanced by the secular military. The Mallorean Grolims were ruled by Urvon, a Disciple of Torak.
The Western Grolims answered to the Sorcerer Ctuchik, another Disciple of Torak, who ruled from Rak Cthol. Later they were led by Agachak. In the west, Grolim power was nearly absolute, particularly among the Murgos and Thulls. However, their hold on the Nadraks was weak at best.
The Grolims had a ranking within the church, which was shown by the color of the linings of their hoods. Low-ranking Grolims had plain black linings or "unadorned hoods" (King of the Murgos:11), middle-ranking priests had green, and the highest rank had purple. There were also assorted High Priests, some of whom had formidable power as sorcerers.
The head Grolim of any particular city was the hierarch. They only answered to Torak's disciples.
Apparently the song of the Orb of Aldur drew every Grolim of the purple towards it.
Grolims sacrificed people to Torak. Most of the time those sacrificed were slaves, but for important rituals Grolims did not hesitate to sacrifice other Grolims to Torak. Because of this centuries long reign of terror, Grolims were feared and despised by most Angaraks, even the rulers of the Angarak nations.
The ritual of sacrifice was as follows: the victim was taken to Torak's temple. A Grolim took an obsidian knife and cut the victim's chest, taking his or her heart. The body was then thrown away. The heart was plunged by the Grolim into the Eternal Fire as a gift to Torak's hunger.
Dedicating and rededicating temples (e.g., if the Sanctum's fire went out) required the spilling of Grolim blood.
Relevance to Prophecies
Belgarath has read the Grolim Prophecies of Rak Cthol, which mention about the war between the King of the East and the King of the South. It also mentioned about the need for an Angarak king and the sacrifice at the Place Which Is No More.