Pura started as the LG God of Order and Light, and his devotion to these beliefs garnered the respect of the other Good and Neutral gods. They came to defer to him in all things and soon accepted him as their leader.
This ended up being his downfall, for his newfound status eventually began to fray his sanity. As the saying goes “Power corrupts, and absolute power corrupts absolutely”, and Pura was no exception. In a fit of paranoia, he waged war against the other gods, starting a conflict spanning 663 years. The war was ended when the Evil gods lent Lautalia their power, allowing her to forge a new plane specifically to imprison Pura. After a particularly devastating battle, Lautalia opened a portal to the Abyss, and the gods together banished Pura.
He lives on as King of the Abyss, a Chaotic Evil god that reigns supreme over pure darkness and consuming madness. Every century or so he rattles the bars of his cage, sending the other deities into a panicked frenzy where they check every lock and safeguard to make sure escape isn’t possible. With their attention elsewhere, Pura’s Abysslings are left to roam the Material Plane unchecked.