Rod of Seven Parts

Mordenkainen suspects Vecna will be vulnerable while he weaves his ritual and If you confront and weaken him, it may be possible to interrupt his ritual. His plan to remake the multiverse would fail. There is an artifact that is, he believes, is the only way to weaken Vecna so that the ritual can be interrupted. It’s called the Rod of Seven Parts. Unfortunately, its component pieces are scattered across existence. The first piece of the rod can be found in The Lost Caverns of Tsojcanth, Tasha's former lair. Once you locate the first piece, the magic inherent in the artifact will point you to the second piece, and then to the third, and so on.