An additional cost is a cost listed in a spell’s rules text, or applied to a spell or ability from another effect, that its controller must pay at the same time that player pays the spell's mana cost or the ability's activation cost. A cost is an additional cost only if it's phrased using the word "additional."
- Additional Cost
- A cost a spell may have that its controller may pay (or, in some cases, must pay) in addition to its mana cost to cast that spell. See rule 118, “Costs,” and rule 601, “Casting Spells.”
- 118.8. Some spells and abilities have additional costs. An additional cost is a cost listed in a spell’s rules text, or applied to a spell or ability from another effect, that its controller must pay at the same time they pay the spell’s mana cost or the ability’s activation cost. Note that some additional costs are listed in keywords; see rule 702.
- 118.8a Any number of additional costs may be applied to a spell as it’s being cast or to an ability as it’s being activated. The controller of the spell or ability announces their intentions to pay any or all of those costs as described in rule 601.2b.
- 118.8b Some additional costs are optional.
- 118.8c If an effect instructs a player to cast a spell “if able,” and that spell has a mandatory additional cost that includes actions involving cards with a stated quality in a hidden zone, the player isn’t required to cast that spell, even if those cards are present in that zone.
- 118.8d Additional costs don’t change a spell’s mana cost, only what its controller has to pay to cast it. Spells and abilities that ask for that spell’s mana cost still see the original value.