Additional cost
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."
Functionality
- See also: Total cost.
Additional costs may be mandatory or optional. Mandatory costs sometimes help determine part of the spell's effect — for instance, a discarded card's properties may affect the power level of the spell. Optional costs often increase the power level or utility of the spell. Additional costs can include mana (but this does not make them part of the spell's mana cost) or other actions. They are usually part of the spell's own design, not applied by external effects, in contrast to miscellaneous cost increases.
Additional costs are added to a spell's mana cost, or alternative cost if one is used, as part of determining its total cost. A spell may have multiple additional costs, which are all added cumulatively. Miscellaneous cost increases and decreases may apply as well. Mandatory additional costs must still be paid even if the spell is cast "without paying its mana cost" (a form of alternative cost); optional additional costs may also be paid if desired in this case, even if those costs include mana.
Rules
From the glossary of the Comprehensive Rules (June 7, 2024—Modern Horizons 3)
- 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.”
From the Comprehensive Rules (June 7, 2024—Modern Horizons 3)
- 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.
Additional cost keywords
This is a list of additional costs that exist as keywords.
Keywords that use linked abilities to achieve a wide variety of effects:
Keywords that increase the spell's power if an additional cost is paid:
Keywords that increase the spell's utility if an additional cost is paid: