God, I hope it's not Omega. That would be stupid, and way out of left field.

I'm thinking/hoping it's the Valeyard/Dream Lord again. But, that voice in the TARDIS....why do I know it? It sounds familiar, but I can't place it. It's not Davros, unless they've recast. I'm thinking it has to be someone we already know, as they have to resolve it next week. Hmmm....