Lord Hayagreeva, the horse head and human body form is the avatar of Akhilanda Koti Brahmanda Nayaka, Shriman Narayana.

Lord Hayagreeva, the half-horse half-human form of Paramatma is the guru and devata for the Rujus.  The Rujus are highly elevated Gods and include Brahma, vayu, latavya,etc totaling to hundred in numbers. Lord Brahma happens to be the first in rank amongst the Rujus and was entrusted the job of creating the universe. Also he was made the ruler of the Satyaloka. 

Lord Hayagreeva imparts Gyana to all the Rujus including Brahma and elevates the Rujus to their next rank and creates new positions for the Rujus.

Lord Hayagreeva Jayanthi falls on Shravana -Poornima and the Aradhana of Sri Guru Raghavendra Swamy is just two days after the Lord Hayagreeva Jayanthi. It is believed that Sri Guru Raghavendra Swamy was performing the Japa of lord Hayagreeva when Sri Appannacharya delivered the Guru Stotra which was concluded by the Guru himself with the words – ‘Sakshi Hayasyotra hi’.