Sri Guru Raghavendra performed penance at a place called Panchamukhi, near Mantralayam, in present day Andhra Pradesh where He received darshan of Hanuman in the form of Sri Panchamukha MukhyaPrana. Sri Guru Raghavendra is considered by his devotees to be a reincarnation of Prahlada, the devotee who was saved by Vishnu in his avatar as Narasimha (see Vaishnava Theology).
Prahlada in turn is believed to be a reincarnation of Shankukarna, a Devatha, in the Dwapara Yuga. Hence, Sri Raghavendra Swamy chose Mantralayam as the location of his Brindavan