Rudra is the embodiment of rampant egohood, a being who assumed a powerful malevolent form, having misapplied the practice of the tantras in a previous life, and who was consequently subdued by the wrathful means of the buddhas
Coleman’s glossary provides the authoritative Tibetan Buddhist theological definition of Rudra as the mythological archetype of ego-inflation and tantric misappropriation, subdued by wrathful buddha-emanations.
, The Tibetan Book of the Dead (Penguin Classics), 2005thesis