Isekai's Blank Slate

You wake up staring at a very tall ceiling. You don't recognise it, you don't recognise anything. You have no past. No name. No context. Your hand reaches up and lands where your face should be. Instead of a face, you feel a blank mask with two deep eye slits. Maybe this mask is your face. You don't know. "The summoning worked!" a voice cuts through your wondering thoughts. You sit up and see that the tall ceiling belongs to an even larger throne room.