When Game of Thrones’ Maisie Williams signed up for a guest spot on the upcoming season of Doctor Who, all we knew was that, in the words of Steven Moffat, she’d be playing a character who will “challenge the Doctor in very unexpected ways.†Now we’ve got our first glimpse of Williams in costume for the role, and lo and behold, the unexpected ways she’s challenging the Doctor include “wearing a mask†and “riding a horse.†No Needle, though, so the Doctor remains safe for the time being.