Agni (Fire) must not burn in his presence; the Maruts (Winds) must blow only as he wishes.

He cannot be hurt by gods or demons.

So Vischnu becomes incarnate as Rama and the gods become incarnate as Monkeys, in order to destroy him.

Such vast power was supposed to be attained by piety without morality.
The Puranas are derived from the same system as the epic poems, and carry out further the same ideas.

Siva and Vischnu are almost the only gods who are worshipped, and they are worshipped with a sectarian zeal unknown to the epics.