Hayagriva
Hayagriva (Skt. Hayagrīva; Tib. རྟ་མགྲིན་, Tamdrin; Wyl. rta mgrin) — the wrathful manifestation of Avalokiteshvara who symbolizes enlightened speech, usually depicted as red in colour and with a horse's head protruding from his crown.
Hayagriva is one of the eight principal deities of Kagyé and referred to as Péma Sung (Wyl. pad ma gsung), 'Lotus-like Speech', in this particular mandala.
In the Longchen Nyingtik, the Hayagriva practice related to Palchen Düpa is called "The Play of the Three Realms" (rta mgrin khams gsum rol pa).