If skin invasion is put on a creature, it's forced to attack. However, the release notes say it's controller is not forced to pay any costs. Is this true of all costs or just mana costs? If so how is this different from bonded construct from origins?
Youâre asking about a few things here, so letâs back up and discuss a some concepts first:
Sometimes creatures are required to attack or block. These are called requirements. When you declare attackers or blockers, you have to fulfill as many requirements as possible.
Some creatures canât attack or block at all. Some creatures canât attack or block unless certain conditions are met. These are called restrictions. When you declare attacks or blockers, you canât violate any restrictons.
Costs to Attack or Block:
Costs to attack or block are a type of restriction, since they prevent the creature from attacking or blocking unless mana, life, etc. is paid. Youâre never required to pay a cost to attack or block, even if you could.
So, whenever you declare attackers or blockers, you have to obey as many requirements as possible while not violating any restrictions. This can have some odd results. For example:
Your only creatures are Bonded Construct and Runaway Carriage. Bonded Construct is enchanted with your opponentâs Skin Invasion, which says that it has to attack each combat if able.Â
Itâs now your turn, and youâre about to declare attackers. What are your options? Well, we have a requirement for Bonded Construct to attack, but also a restriction that it canât attack alone. Letâs look at the possibilities here:
If you donât attack with any creatures, then youâre not meeting the requirement, but youâre not violating the restriction.
If you attack with just Runaway Carriage, then youâre not meeting the requirement, but youâre not violating the restriction.
If you attack with just Bonded Construct, youâre meeting the requirement, but violating the restriction.
If you attack with both creatures, youâre meeting the requirement and not violating the restriction.
Since thereâs an option that both meets the requirement and doesnât violate the restriction, you have to go with that option since it maximizes the number of met requirements. This means that your Carriage (which you were saving for later) and your Construct both have to attack here.