If they are blind however, are they going to be able to fight?
Mechanically, I'd run it as a declaration of
I'm Covering My Eyes or equivalent. Opponents will almost certainly invoke for effect / compel at which point they can use Stealth or possibly even Athletics to set up a block against targeting. The 'blind' attackers will need to set up declarations (I'm Listening), maneuvers (Flanked), use terrain / zone borders (move into the hall), and possibly invoke a few of their own aspects to break through the block and hit.
Basically, you give yourself a disadvantage and set up the situation to help overcome it. It's worth noting, the attackers probably get at least one fate point by self compelling (or being compelled) the Not Looking declaration.