The Rift

The Rift is a great scar upon the world and it is filled with demons.

GEOGRAPHY

The Rift is a massive scar upon the world. This scar goes down a thousand miles to a bed of even deeper black ooze. It is one hundred miles across at its widest point and stretches for about five hundred miles. The Rift is a place of two sides ... northeast and southwest that each round out then come together in sharp points at the northwest and southeast corners.

WHAT IS THE RIFT?

The Rift was made by the gods. The gods had to remake the world after the demons, creatures of chaos, destroyed the world in their reckless abandon. Furious with the demons, the gods then made The Rift and collected every scrap of the demons into a vast ooze they put at the bottom of The Rift. Beings of chaos, demons do not stay destroyed, always coalescing back together even if it takes eons to do so, which was why the gods mashed them all together into an ooze. The gods then sealed The Rift with great magic that prevented anything demonic from crossing it.

The demons, all mashed together, churned and swam, their individual bits of essence fighting and devouring each other to grow. As they grew, so did their minds, until the first ones to realize they could leave the ooze did so. As these near mindless demons crawled up the sides of The Rift, they claimed perches near the ooze where they could attack and devour others who climbed out. And, so, over time, some demons returned only to find themselves trapped within the confines of The Rift. With limited space, the battle for domains consumes the demons. Those that aren't completely devoured or are torn apart in combats will have their bits returned to the ooze. With The Rift naturally formed into two parts, whatever side a demon crawls out of the ooze on is the side it must fight for against the other side with the bigger, stronger demons dominating the smaller ones.
Some demons care more about escaping The Rift than fighting for territory and rank. It is these demons who dig and work at magics to find ways to escape. And, now and again, they do, though usually with help from a sorcerer. When these demons are killed, its still back to the ooze.