Great Rift

Great Rift is a chasm that runs next to the new dwarven capital, Feo Jera.

Background
For the longest time, this natural barrier had protected Feo Jera from all manner of monstrous attacks. The dwarves could thwart any monsters from the west who tried to invade so long as they defended the suspension bridge which ran across the Great Rift. However, nobody knew what was down there, and nobody had returned alive from the two expeditions that the Dwarf Kingdom sent out to investigate it.

The Craftsman of Dwarf Arc
The Great Rift was the last line of defense that prevented the Quagoa from crossing and taking the dwarven capital. However somehow the Quagoa led by Yozu managed to find a way around the obstacle and invaded the fortress guarding the rope bridge. The Dwarves at the other end of the gorge were pushed back to the fortress that led to the city as they were pushed back by the huge numbers of the Quagoa.

Just as the Quagoa crossed the suspension bridge and were preparing to break trough the fortress gate, They were taken aback when the gates were opened and two of Ainz's Death Knights came out and started to slaughter the invaders. They were forced back the suspension bridge with sheer amount of heavy losses from the Death Knight's attacks. Yozu sensing their defeat pulled back his remaining troops and ordered the suspension bridge that connected both sides of the rift to be cut down, so as to prevent the enemy from coming to their side.

While successful in eliminating the two Death Knights, the Quagoa suffered heavy losses and their path to the dwarven capital was cut off, forcing Yozu to fall back to report back in what just happened.

Ainz Ooal Gown would later travel to back to the Great Rift to secure the dwarven fortress.

Layout
It referred to the huge chasm that ran along the western side of the Dwarven Capital, Feo Jera. It was a massive crevasse, over 60 km long and 120m across at its narrowest point. Its depth was unknown.

Trivia

 * Ainz Ooal Gown wishes to do an in-depth investigation of the Great Rift, believing unknown monsters and ores to be found there.
 * In volume 11, it was never explained how the Quagoa managed to circumvent the Great Rift.