Mahabali legend - and ONAM festival
According to Hindu mythology, Mahabali was the great-great-grandson of a Brahmin sage named Kashyapa, the great-grandson of a demonic dictator, Hiranyakashipu, and the grandson of Vishnu devotee Prahlada.
Onam is a "popular major Hindu festival in Kerala" : Cultural festival with much zest alongside Hindus
This links the festival to the Puranic mythology of Prahlada of Holika fame in Hinduism, who was the son of Hiranyakashipu. Prahlada, despite being born to a demonic Asura father who hated Vishnu, rebelled against his father's persecution of people and worshipped Vishnu. Hiranyakashipu tries to kill his son Prahlada, but is slain by Vishnu in his Narasimha avatar, Prahlada is saved.
The dwarf Vamana taking a leap-step is a part of many Hindu temple arts (above), and one legend behind Onam. Prahlada's grandson, Mahabali, came to power by defeating the gods (Devas) and taking over the three worlds. According to Vaishnavism mythology, the defeated Devas approached Vishnu for help in their battle with Mahabali.
Vishnu refused to join the gods in violence against Mahabali because Mahabali was a good ruler and his own devotee. Mahabali, after his victory over the gods, declared that he would perform a Yajna (homa sacrifices/rituals) and grant anyone any request during the Yajna. Vishnu took the avatar – his fifth – of a dwarf monk called Vamana and approached Mahabali. The king offered anything to the boy – gold, cows, elephants, villages, food, whatever he wished. The boy said that one must not seek more than one needs, and all he needed was "three paces of land." Mahabali agreed.
Vamana grew to an enormous size and covered everything Mahabali ruled over in just two paces. For the third pace, Mahabali offered his head for Vishnu to step on, an act that Vishnu accepted as evidence of Mahabali's devotion.
Vishnu granted him a boon, by which Mahabali could visit again, once every year, the lands and people he previously ruled. This revisit marks the festival of Onam, as a reminder of the virtuous rule and his humility in keeping his promise before Vishnu. The last day of Mahabali's stay is remembered with a nine-course vegetarian Onasadya feast.
The name Thrikkakara is originated from 'Thiru-kaal-kara' meaning 'place of the holy foot'. The main deity at Thrikkakara Temple is Vamana, the smaller temple to the side has Shiva as the deity. Vamana temple is known as 'Vadakkum Devar' and the Shiva temple is known as 'Tekkum Devar'. A number of subsidiary deities have been installed at Thrikkakara Temple.
The 1961 census report on the Onam festival states: Though the Vamana temple is accepted as the main temple at the elite level, the local people consider the Shiva temple as the more important one. They believe that Shiva was the 'Kuladeivam' (family deity) of Mahabali and that there was no Vamana temple at that time.
The palace of Mahabali was situated at the place where the Vamana temple is at present. After the fall of Mahabali, his palace was destroyed and later on Vamana was installed on that spot by the saint Kapila. According to Nanditha Krishna, a simpler form of this legend, one without Mahabali, is found in the Rigveda and the Vedic text Shatapatha Brahmana where a solar deity is described with the powers of Vishnu.
This story likely grew over time, and is in part allegorical, where Bali is a metaphor for thanksgiving offering after a bounty of rice harvest during monsoon, and Vishnu is the metaphor of the Kerala sun and summer that precedes the Onam.
According to Roshen Dalal, the story of Mahabali is important to Onam in Kerala, but similar Mahabali legends are significant in the region of Balia and Bawan in Uttar Pradesh, Bharuch in Gujarat, and Mahabaleshwar in Maharashtra.
The story is significant not because Mahabali's rule ended, but it emphasizes the Hindu belief in the cyclical nature of events, that no individual, no ruler and nothing lasts forever, except the virtues and self-understanding that overcomes all sorrow.