Chime of Exile
a magical trinket shown to us by Mordenkainen, who claimed that it could be used to banish Vecna if we had the Rod of Seven Parts.

Rod of Seven Parts
a rod that was originally created eons ago to imprison the wolf spider Miska to the plane of Pandemonium. Before it was shattered into pieces and spread across the multiverse, it was called the Rod of Law. The first piece was located in Web's Edge in the lair of a spider dragon; the second in the Astral Sea, inside the stomach of a lizard-like monster aboard the Lambent Zenith.