Quote Originally Posted by FourDogsinaHorseSuit View Post
But that's not what happened. To declare an attacker requires you to

You're under the impression that declaring attackers is a thing done and then the game does stuff when the rules say that declaring an attacker is a process. You check the object all throughout this process. When you started the process it was a 2/2 to get under bridge, but by the time you're checking for triggers the process has made it a 6/6 with abilities.
The tapping is essential to making this work, because the order of steps matter.
It would certainly make Mask better if it worked like you‘re saying, but there is a hole in the rules. The problem is a logical one of what the game object was when a player declared it an attacker. Yes all the replacement effects happen before priority is given, and all the replacement things are done in a no-priority batch.

Ensnaring Bidge isn‘t quite the right card to illustrate this concept. Most specifically E-Bridge states creatures with power greater than x may not be declared an attacker, and this has nothing to do with removing things already past declaration of attack. To illustrate: Geist of St. Traft attacking into a Bridge (2 cards in hand), defender gets whacked for 6.

Perhaps a better way illustrate the difference between the game object which was declared the attacker and what game object is treated as tapped and attacking would be this:
Suppose a card imposes a static tax on any game object over 2 power attempting to declare an attack; at no point would the Mask‘d 2/2 owner be required to pay said tax (in that combat) by flipping over into the 6/6.

Another example could be a card that has a ferocious clause and will generate 2 types of triggers, one for attacking with <4 power and a different one if the attacker was over 4 power. With the face-down 6/6 you would only get the trigger for a 2/2 stat line.