Origin story
Indilayappan is the presiding deity of the ancient Avanavanchery temple near Attingal in Thiruvananthapuram district. Temple tradition identifies him with Shiva and Umamaheswara, and devotees approach him for good health, courage and relief from hardship.
The shrine is counted among the oldest temples of Kerala and keeps a cluster of sub-deities, including Unni Ganapathy, Dharma Sastha and the Naga devathas, with a separate sanctuary for Mallan Thamburan. Its quiet rituals preserve a form of worship that reaches back to the old Venad country.
Source: Wikipedia: Avanavanchery Sri Indilayappan Temple — https://en.wikipedia.org/wiki/Avanavanchery_Sri_Indilayappan_Temple