Huh
Missy not dead
Yet
Daleks
Check
Zygons
Well , we saw them a couple years ago in Day of the Doctor so...
Lot of unknowns
And
Arya Stark
No, not really
But, really, Maisie Williams, playing someone probably not insignificant, based on her look and position in the trailer. Speculation is already running rampant. Romano? Susan? Jenny? Hell the show has a background of stuff going back further than Trek, and way more episodes. My money is on Jenny. Susan and Romano, while possible, are not characters the average viewer would remember. But Jenny was created in the Tennant era, so still in people's memories
Know in September
