MTG Keyword Rules — Comprehensive Rules Glossary

Teamwork represents a static ability that functions while the spell with teamwork is on the stack. “Teamwork N” means “As an additional cost to cast this spell, you may tap any number of creatures you control with total power N or more.” Paying a spell’s teamwork cost follows the rules for paying additional costs in rules 601.2b and 601.2f–h.

Abilities may refer to a spell cast “using teamwork” or similar. Such phrases refer to whether the player who cast the spell declared the intention to pay the spell’s teamwork cost as they cast that spell.

If part of a spell’s ability has its effect only if teamwork was used to cast it, and that part of the ability includes any targets, the spell’s controller chooses those targets only if teamwork was used to cast that spell. Otherwise, the spell is cast as if it did not have those targets. See rule 601.2c.