A wrathful deity. In the Nyingma lineage also known as Pema Wangchen (pad ma dbang chen) or Pema Sung (pad ma gsung).
He is one of the main deities in the eight teachings of Drupde (sgrub sde), the section of accomplishment in the Mahayoga, and the main deity of the secret speech section.
The Nyingma Gyu Bum (rnying ma rgyud 'bum) contains several tantras related to Hayagriva.
A description of a Hayagriva mandala can be found in the Pema Wangchen Yang Sang Tro Pay Gyu (pad ma dbang chen yang gsang khros pa'i rgyud). Hayagriva as the central figure is surrounded by Vajramahendra in the east, Ratnamahendra in the south, Padmamahendra in the west, Karmamahendra in the north, and Ankushi, Pashi, Sphoti and Ghanta in the four gateways of the mandala.