Blue caste

The Blue Caste were an order of Sorcerers from the East.Little was known about them except that they had joined Saurons's cause in the war of the ring against the orders of their supposed leader, Yirokhsar the Blue, and they were the true head behind the Khundolar invasion, them having corrupted and influenced the easterlings warrior-chiefs.

The blue caste was in itself split into two factions, the brotherhood of the mind and the brotherhood of the spirit.