The Grey Temple is an ideology among necromancers which centers upon power and control, ownership and domination. Grey Temple necromancers believed that by possessing power over life and death, they deserve the whole World of Life. Grey Temple theology differs from Green Temple at these points.
The Grey Temple started as an ideology, taught by some priests. Later, entire temples would form around Grey Temple philosophy.
Durring the Golden and Second ages, necromancy continued to evolve. Though Grey Temple theology did exist during the Mage Wars, it was only a philosophical disagreement until the begining of the Third Age. Before then, very few dedicated Grey Temples existed, with most temples following a dual ideology or fully identifying with Green Temple beliefs.
The schism began in the early Third Age as changes in the political climate of the Alliance opened up new lands. Milennia-old disagreements which had little to do with ideology caused many temples to divide.
With nearly all temples now identifying with either Grey or Green Temple theologies, the stage was set for an apocalyptic war. See Necromanic Wars, terminated by Lal Soratami. Remnants of the Grey Temple continued in the Dark Order; but these wielded no interplanetary power.