Lord Ayyappa had his human incarnation as the son of the King of Pandalam, Kerala. At that time, the kingdom of Pandalam was under the rule of Raja Rajasekhara. During one of his hunting expeditions, the wails of a child on the banks of the River Pampa puzzled him. As he moved in the direction of the voice he found a resplendent and helpless infant there. The beautiful baby with a radiant face had a gemstone around his neck, hence the name Manikantan ("Mani", means gemstone and "kantan" means wearer around the neck). Manikantan was born of Hari (Lord Vishnu) and Hara (Lord Shiva), with Hari assuming the form of a female (Mohini). Hence Ayyappan is also named as Hariharasutan (Sutan meaning Son).The king had no children, though he was pious, charitable, just, and God-fearing. The king and the queen were the ardent devotees of Lord Shiva and Lord Vishnu respectively. They had prayed to their respective deities for blessings in the form of a child. So the King accepted the child as God's gracious gift to his fervent prayer for an heir to his throne. Manikantan was given proper education and training and he grew into a boy well versed in academic lore and martial arts. Meanwhile the Rani (Queen) gave birth to a son; however the king regarded Manikantan as his elder son and decided to crown him as the Yuvaraja.
Since the minister of the Raja was against Manikantan becoming the Yuvaraja, for several hidden reasons, he along with his sycophants lured the queen to act against the king's decision to coron Manikantan. On the coronation day of Manikantan as Yuvaraja, the queen pretended to be suffering from unbearable stomach ache, and said that she was unable to get any relief from the treatment of any doctor. Finally came a fake practitioner and prescribed "the milk of a tigress" as the cure of the queen's illness.This drama took place at the instance of the minister. The king appealed to everyonel to get the tigeress-milk, but no-one dared, as all feared death. At last, Manikantan came forward and went to the forest in search of tigress milk, despite the king's attempt to stop him as he was deeply frightened that the deemed Yuvaraja may not come back alive.
Manikantan entered the forest to fulfill his divine duty, to rid from the world, the demoness, Mahishi. Manikantan killed her and released a beautiful woman who had been cursed to become Mahishi. The young woman asked Ayyappan for his hand in marriage, but being a celibate he declined. However he promised that she would be visited by pilgrims and would be housed next to his temple, and if ever the number of new pilgrims (Kanni Ayyappan) stopped visiting him then he would marry her. Hence she is now worshiped as Maalikapurathamma.
On the death of Mahishi, Indra - the king of the gods, who was displaced and banished by Mahishi, led several tigers for the disposal of Ayyappan.
Days later Manikantan entered the palace precincts riding a fierce tigress and followed by a pack of her cubs. The schemers were frightened and confessed their plot. They were convinced of his divine origins, and prayed to him to be with them for their own salvation and for the safety of the kingdom. Immediately Manikantan disappeared. The king took a decision that he would not eat anything till Manikantan came back. Then Manikantan gave a darshan to the king.
Filled with emotions of happiness, grief, fear, wonder and 'Bhakti' (devotion to God) and self-surrender, the king stood praying for the mercy and blessings of Manikantan. He repented that he could not fully visualize the truth of the divine powers of the Lord and repeatedly requested him to forgive him for behaving as if he were his son only. The Lord lovingly embraced the King who prayed to bless him by freeing from ego and the worldly life of birth and rebirth and granted Moksha (salvation). He told the King that he was destined to return. The king requested Lord Manikantan to allow him to build a temple and dedicate it to him and the Lord assented.
Manikantan then enlightened the King on the path of attainment of Moksha. The Lord shot an arrow that fell at the top of Sabrimala and told the King that he could construct a temple at Sabarimala, north of the holy river Pampa and install His deity there. Ayyappan also explained how the Sabarimala pilgrimage shall be undertaken, emphasizing the importance of Penance vratham and what the devotees can attain by His 'darshan'.
The King secured a promise from the Lord that on Thai Pongal on January 14, every year (celebrated as "Makara Jyothy" all his personal jewellery (usually kept at the Palace) will be adorned on his image at Sabarimala. Hence on the 12th of January every year, the Jewellery will be taken on foot from the Palace by a special emissary of the kingdom, after the puja with all pomp, devotion and reverence. Immeditely when the Arti is over, Royal Garuda (Eagle) flies over the Palace. The Royal Garuda flies ahead, and appears as though guiding the pilgrims throughout their journey. Since there was no modern means of communication like Telephone or Mobile, to the hundreds of thousands of Devotees desirous of worshipping Lord Manikantan's Jewels enroute to his Abode, this Garud was the sole and absolute signal of advance information even to the Temple authorities at Sabarimala to get ready for the adorning of the Jewels. This journey on the 12th and 13th of January finally reaches Sabarimala on January 14th. Immediately after the jewellery is adorned on the Deity, there is an Aarti (offering by burning Camphor). The miracle is that just after the Arti, without loss a second, the Jyothy appears on the east side of the Temple up above the Hills. But then the Lord further consoled the King saying that the devotees who held him and his descendants in 'Bhakti' shall happen to be devoted to Him as well. Manikantan then blessed the King and all others assembled there, and vanished. The King duly constructed the temple at Sabarimala, dedicated to him. The deity for installation was prepared by Parasurama, believed to be an incarnation of Lord Vishnu, and was installed by him.