Lord Ayyappa is a unique deity born from the union of Lord Vishnu (as Mohini) and Lord Shiva. He is especially revered in Kerala and is the presiding deity of the famous Sabarimala temple.
As Hariharaputra (son of Hari-Vishnu and Hara-Shiva), he represents the unity of Vaishnavism and Shaivism. His worship requires a 41-day Vratam (penance) before visiting Sabarimala.
Ayyappa is the eternal Brahmachari (celibate) and is worshipped for discipline, devotion, and protection.