A greatsword lost in the land of Washington D.C., recoverd by the Company of the Red Spear from West End. It was a sentient item, possessed by the soul of a woman from long ago. It claimed to be from a town called Sigil somewhere in the planes.
Will Dreadbane plunged Eve into the soil at a nexus of the demiplane of Dread, the demiplane of Shadow, and the Prime Material Plane. This eventually consumed Eve, and ended in Will's torture and death. It saved the Prime Material plane from destruction however.