Great though Sandy's Sorcery rules are, they don't give any explaination of the different sects. Below is a brief synopsis of those sects for which i have found more information. If you can fill in some of the gaps please email me.
Believe law of Malkion does not apply
to chaotic beings – who they tap freely.
Found now mainly in central Ralios.
They are immortal, so long as they
perfectly maintain their ancient strictures.
To maintain these strictures
they separate themselves from the rest of humanity. They apy no heed to the law of Malkion and tap without
restriction – yet they claim to be the oldest and most perfect followers of
Malkion.
Culture based upon a Malkioni feudal
culture with worship of other Gods emphasised above the Invisible God.
Allow tapping of non-Malkions.
They also believe in Reincarnation.
Most live in Ralios.
Live in a society of four castes.
They believe that each individual should rise through all four: Farmer,
Knight, Wizard and Lord. They
dominate Fronela and are found in NW Pamaltela.
Heresy within Hrestolism. They believe that progression within the establishment of Loskalm is impossible, as the members of the Wizards and Lords castes in that state are too interested in maintaining their own position. Instead, Perfecti attempt a process of spiritual development and purification to transcend the four aspects – few succeed.
Have a society with four castes similar to the Hrestoli: Farmer, Knight, Wizard and Lord. But they do not believe in mobility between those castes. They dominate SW Genertela and are also found in NW Pamaltela.
Believe anyone causing death cannot make it to paradise.
Combine the worship of ordinary deities with the Invisible God. Exists mainly in Ralios.
Ancient enemies of the Brithini. They are a race of devious atheists who cheat, steal and blaspheme. They do not follow the laws of Malkion. They have become a major naval power, and command the sea routes to Pamaltela. They are immortal, so long as they obey their rules – including insest, promiscuity, murder, etc. They are present in all Western ports, though they are confined to ghettos.
Worship pagan Deities of the Eastern Isles as saints. Only found in the Eastern Isles.
Claim to be descended from a bastard son of Malkion and a mermaid. They have webbed fingers and toes and green or blue skins. They worship merman ancestors as well as various spirits of the seas, in adition to the Invisible God.
Sources: Gods of Glorantha (Avalon Hill) and Tales of the Reaching Moon #13.