Their supreme being is known as Yasdan. He is considered to be on such an elevated level that he cannot be worshipped directly. He is considered a passive force, the Creator of the world, not the preserver. Seven great spirits emanate from him of which the greatest is the Peacock Angel known as Malak Taus – active executor of the divine will. The peacock in early Christianity was a symbol of immortality, because its flesh does not appear to decay. Malak Taus is considered God’s alter ego, inseparable from Him, and to that extent Yazidism is monotheistic.
There is more here, interesting throughout.