Blood Rift

The Blood Rift was the rift that the River of Blood created when crossing the planes.

Description
The Rift served as the main connection between the Nine Hells and the Abyss, so it was the main battlefield for the Blood War. In addition, it sometimes connected to other lower planes, bringing the eternal struggle there, until it floated away or a deity took action to stop the carnage.

The Blood Rift was very similar to the Barrens of Doom and Despair, with empty plains and rocky badlands, perfect for ambushes and treachery.

History
Some time during the Hundred Years of Chaos, the Blood Rift was folded into the Abyss.