The Mummy's Ghost is a 1944 film, a sequel to The Mummy's Tomb, and Chaney plays the Mummy again. John Carradine plays the new high priest, sworn in by the old high priest George Zucco (from previous films).
It's not unforgivably bad, I don't guess, except that I keep thinking Chaney is capable of more than bandaged foot-dragging. You do have to be willing to accept as a sequel something that over-writes the elements of previous films, but I'm used to that by now. John Carradine is the stand-out here.
Moria says, "It is routinely handled on all levels." 1000 Misspent Hours concludes with this:
The Mummy’s Ghost disarms any attempt at such an enterprise with a kind of confrontational candor. “Yeah, I’m stupid,” it says, “You got a problem with that?!”TCM has an overview.