Tapping Before the Attack
BeginnerIcy Manipulator against the attacker — but only in the right step.
Cards involved
The attack is coming
It's your opponent's turn and they are about to attack with Hill Giant. You control Icy Manipulator and want to stop that.
507.1First, if the game being played is a multiplayer game in which the active player’s opponents don’t all automatically become defending players, the active player chooses one of their opponents. That player becomes the defending player. This turn-based action doesn’t use the stack. (See rule 506.2.)
What happens?
When do you have to tap?
What is your last window so the Giant can't attack this turn?
Pick an answer to continue.
Declaring attackers is a turn-based action at the very start of the step — there is no "in response" BEFORE it. Your last priority window is the beginning of combat step (507.1). And: tapping a creature AFTER it's been declared doesn't remove it from combat and doesn't prevent its damage.
508.1First, the active player declares attackers. This turn-based action doesn’t use the stack. To declare attackers, the active player follows the steps below, in order. If at any point during the declaration of attackers, the active player is unable to comply with any of the steps listed below, the declaration is illegal; the game returns to the moment before the declaration (see rule 733, “Handling Illegal Actions”).
You activate at beginning of combat
Icy Manipulator taps the Hill Giant. The ability can be responded to — but your opponent has no answer.
Declare attackers
The tapped Giant can't be declared as an attacker (508.1). No attack this turn.
508.1First, the active player declares attackers. This turn-based action doesn’t use the stack. To declare attackers, the active player follows the steps below, in order. If at any point during the declaration of attackers, the active player is unable to comply with any of the steps listed below, the declaration is illegal; the game returns to the moment before the declaration (see rule 733, “Handling Illegal Actions”).
Stack
Icy Manipulator
, 
: Tap target permanent
Hill Giant
Your opponent's 3/3 — about to attack
Activated ability: Icy Manipulator
Icy Manipulator ability — target: the Hill Giant
The stack is empty.
Battlefield
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