My opponent had on the battlefield a Swarm Guildmage and three other creatures. My opponent then enters Combat and declares his three other creatures as attacking.

After this happens I then declare two of my creatures as blockers, each blocking one of his creatures, to which then he responds by activating Swarm Guildmage's ability that grants each of his creatures Menace. His argument is then that, because now his creatures have Menace, my blocks are illegal and I have to re-assign blockers.

My assumption is that once blockers are declared then no matter what happens afterwards during combat the blockers initially declared would remain legal.

Is this true, or is it that my opponent was correct and my blockers suddenly became illegal after the activation? If so, are there any other scenarios in which a blocker can be made illegal after being declared as a blocker?


2 Answers 2


Your friend is wrong. His creatures are blocked.

Blocking goes through a series of steps outlined in rule 509. The first step is declaring blockers (509.1). To sum up, you declare which creatures are blocking, what they are blocking, check any restrictions and pay any costs. At the end of all that we get to 509.1h:

509.1h An attacking creature with one or more creatures declared as blockers for it becomes a blocked creature; one with no creatures declared as blockers for it becomes an unblocked creature. This remains unchanged until the creature is removed from combat, an effect says that it becomes blocked or unblocked, or the combat phase ends, whichever comes first. A creature remains blocked even if all the creatures blocking it are removed from combat.

That's it. Your opponents creatures are blocked. The only chance he has to activate abilities or cast spells are once he receives priority which comes much later (outlined in 509.4). Once 509.1h happens, restrictions (like menace or flying or whatnot) are never checked again. And since nothing in Swarm Guildmage's effect instructs you to make a creature unblocked, those creatures are still considered blocked.

If your opponent wanted to use Swarm Guildmage's ability to give his creatures menace and have that effect blocker legality, the last chance he has to do so is after attackers are declared and each player gets priority but before the declare blockers step starts.

  • 4
    Might be helpful to point out what was the latest point his opponent could have activated Swarm Guildmage's ability that would actually have an effect. Is it before he announces he's attacking? Before he decides which creatures he's attacking with? Is there a point after he's declared attackers, but before blockers have been declared that it could worked? Commented Nov 1, 2018 at 22:01
  • 3
    Technically, they do have Menace. They are still considered blocked, so this changes nothing. But they technically have Menace.
    – John Doe
    Commented Nov 1, 2018 at 23:33
  • Restrictions on blocking (including evasion abilities) are checked in 509.1b, and only then. Once the process of blocking has made it past that step (and not restarted because it fails a later step, like disobeying "This creature blocks each turn if able") evasion becomes meaningless.
    – Arthur
    Commented Nov 2, 2018 at 7:50
  • @Shufflepants Good idea. Done.
    – Becuzz
    Commented Nov 2, 2018 at 12:51
  • Note that as the active player, the attacking player gets priority first after declaring attackers. This is the last opportunity he has to (reliably) activate the mage. If he passes priority (thinking to lure out some combat tricks first, for instance), and the defending player then passes without playing anything, the game automatically continues to declaring blockers and it's too late to activate the guild mage.
    – Arthur
    Commented Nov 2, 2018 at 16:24

Restrictions on blocking are checked exactly once, during the declare blockers step. Evasion abilities or other restrictions that take effect after that point don't matter, as described by comp rule 509.1:

509.1b The defending player checks each creature they control to see whether it’s affected by any restrictions (effects that say a creature can’t block, or that it can’t block unless some condition is met). If any restrictions are being disobeyed, the declaration of blockers is illegal.

A restriction may be created by an evasion ability (a static ability an attacking creature has that restricts what can block it). If an attacking creature gains or loses an evasion ability after a legal block has been declared, it doesn’t affect that block.

Once a legal set of blockers has been declared, it's too late for players to add restrictions or requirements to it, whether that's through evasion abilities, protection, unblockable effects, Lure effects, etc.

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