The Triune was one of the 2 major cults on sanctuary, several thousand years before the events of Diablo I. The other major cult being the Cathedral of Light. Though appearing to be a peaceful group, the cult was actually a foothold for the burning hells on sanctuary.
The Triune had various temples all over sanctuary, mainly in the eastern lands of sanctuary. All temples were still subordinate to the main temple in Kehjan. The Triune was split into 3 seperate branches, each with its own personification of a prime evil.
Dialon The spirit of determination
Dialon The Stubborn Ram, was really Diablo the Lord of Terror.
Bala The Spirit of Creation
Bala was represented by the symbol of a leaf, infact followers were really worshipping Baal the Lord of Destruction.
Mefis Spirit of Love
Mefis' symbol was a red circle representing the heart infact, worshippers were really following Mephisto the Lord of Hatred.
Each branch was lead by a high priest who, in turn answered to the Primus. The Triune rapidly fell into disarray after the mysterious disappearance of the Primus. In the end, by the combined efforts of Uldyssian and his nephalem followers, the Triune was utterly destroyed.
Richard A. Knaak - The Sin War Trilogy