Once you beat the game, you can choose between 3 endings, with different consequences for each choice.

Die and go to heaven
You unlock the multiplayer dungeon level, The Depths of Jealousy.

Live and fight one forever
Allows you then to start a new game being a dark hero anyone you want rageworf, ravenous etc.

Sacrifice your body for the patapons
You save the Patapons. They are back alive.