Player A attacks with
Breaker of Armies and
Archangel of Tithes. Player B has 3
Wind Drakes. Can Player B disregard BoAs requirement due to Archangels blocking costs, but still block Archangel by paying 3 mana?
Some relevant rules text:
509.1c The defending player checks each creature he or she controls to see whether it’s affected by any requirements (effects that say a creature must block, or that it must block if some condition is met). If the number of requirements that are being obeyed is fewer than the maximum possible number of requirements that could be obeyed without disobeying any restrictions, the declaration of blockers is illegal.
If a creature can’t block unless a player pays a cost, that player is not required to pay that cost, even if blocking with that creature would increase the number of requirements being obeyed.That player B can choose not to pay and thus not to block at all is obvious, but how far does “pay that cost” stretch? Since blocking cost has been payed, is the block illegal because the Drakes are now allowed to block Breaker of Armies? Or is it considered another cost to allow blocking for BoA specifically, comared to paying to allow block of Archangel?