The Ayyappa Mythology
The mythology behind Sastha, artfully explains this amalgam of Vishnu and Shiva. Briefly it is as follows. After a long drawn strife between Gods and demons, they mutually agreed to temporari1y sink their differences and with their combined efforts churn the ocean and draw out nectar (amrita) that existed at the bottom of the oceans. Both the Gods and demons stood on opposite sides and started the churning process with the help of Seshnaga (the celestial cobra) as a rope. The churning went on for and many beautiful and powerful things issued forth from the ocean. All these things were distributed equally between the Gods and demons. At last came the coveted nectar, but as soon I came up, the demons snatched it and ran away leaving the Gods high and dry. The Gods then prayed to lord Vishnu to retrieve their share.
To do this Vishnu struck upon an idea to deceive the demons. He took on the form of an enchanting maiden as Mohini known as the Mohini-Avatara of Vishnu. Mohini approached the demons who were having a loud argument as to how to distribute the stolen nectar amongst themselves . Taking advantage of this confusion Vishnu in the guise of Mohini offerred to distribute the nectar on condition that the nectar also be distributed amongst the Gods.
from the Chola period.
Rajendra Chola was an ambitious ruler.
Under him and under the Shailendra rulers
Indians sailed to the far-east and
established colonies in Java
Sumatra, Bali, etc.
Under the captivating influence of Mohini, the demons agreed and Mohini went about distributing the nectar, first among the Gods. Very deceptively she had made the Gods and demons sit in different rows, such that when the nectar was distributed to the last God sitting there, no nectar would be left for the demons.
Now unknowing to Mohini, her seductive form had captured Shiva's imagination and later he requested Vishnu to reappear as Monini before him. Despite being warned by Vishnu that Mohini was irresistible and that Shiva would fall prey to her charms, Shiva insisted that she appear before him confident as he was of his self-control. But lust being the weakest link in the chain of instincts, on seeing the inviting forn of Mohini Shiva's self-control gave way and out of the union of Shiva and Vishnu (as Mohini) was born Sastha who is a repository of all what Shiva and Vishnu stand for.