Each other player discards an Attack card (or reveals a hand with no Attack cards).
During your Action phase, if you have no Actions remaining, you may play this from your hand.
Other players must discard one and only one Attack card. If they do not have an Attack card, they must reveal their hand for all players to see.
If you are in your Action phase and have used up all your Actions, you may play this out of your hand as though you had +1 Action.
If you do have Actions remaining when you play this, it uses up an Action, as normal.