Costs paid in this way might be: — Riftbound Rules

Section 204 — 16 rules

204.1.: Base Costs: These costs are the most fundamental costs that must be paid to finalize a spell or ability.
204.1.a.: On cards, the Base Cost is found in the upper left corner of the card.
204.1.b.: On activated abilities, the Base Cost is the resource or instruction written before the “:”.
204.2.: Additional Costs: These Costs are in addition to the base cost of the spell or ability and will include “as an additional cost.”
204.2.a.: Additional Costs must be paid to finalize the spell or ability, in addition to the base cost.
204.3.: Costs within Instructions: These Costs are part of the resolution of a spell or ability, and will take the form “[do X] to [do Y].”
204.3.a.: When Costs within Instructions appear as the first part of the effect in triggered abilities, the cost is taken to be the base cost of the triggered ability. It must be paid to finalize the triggered ability. Example: Overzealous Fan is a unit that reads “When I defend, you may kill me to move an attacking unit to its base.” In order to finalize the ability to the chain, its controller must kill Overzealous Fan.
204.3.b.: When Costs within Instructions appear in spells, activated abilities, or in later parts of triggered abilities, the cost must be paid to get the effect during resolution of the spell or ability. Example: Bullet Time is a spell that reads “Pay any amount of [A] to deal that much damage to all enemy units at a battlefield.” As the spell resolves, its controller pays any amount of [A] as a cost, and deals that much damage to all units at a battlefield as the effect. Example: Ancient Henge is a gear that reads “[Reaction][>] [E]: Pay any amount of Energy to Add that much [A].” As the ability resolves, its controller pays any amount of Energy as a cost, and Adds that much [A] as the effect. Example: Insightful Investigator is a unit that reads “When you play me, choose an opponent. They reveal their hand. You may pay 2 XP to choose a card from their hand. If you do, they discard that card and draw 1.” As the ability resolves, its controller may pay 2 XP as a cost, and chooses a card from that player’s hand as the effect.
204.4.: Applied Costs: These Costs are applied to one or more Game Actions, and typically take the form of a passive ability with a Cost within Instructions preceded by “must.” Example: Mageseeker Investigator reads in part “Opponents must pay [A] for each unit beyond the first to move multiple units to my battlefield at the same time.” This is an applied cost.
204.4.a.: The associated Game Action is the linked Effect for the Cost.
204.4.b.: Applied Costs are paid as the Game Action is performed. They do not use the chain and cannot be reacted to.
204.4.b.1.: Abilities that Add resources with the Reaction keyword can be activated at any time when costs need to be paid. See rule 429. Add for more information.
204.4.c.: If a player can’t pay or chooses not to pay the Applied Cost, they cannot perform the associated Game Action.
205.: An instruction that requires a player to pay resources or spend counters or XP that does not also have a linked Effect, is not a Cost. Example: A card effect reads, “When I attack, you may pay [4][C]. If you do, kill a unit here.” Paying [4][C] in this way is not a cost of the ability, base or otherwise, but a game action being performed by a player. The later instruction checks whether the game action was performed, not whether a cost was paid—if paying [4][C] was replaced for any reason, the later linked instruction will not execute.
206.: Effects that need to determine a card’s cost for any purpose always use its printed or copied cost, even if that cost is increased, decreased, or ignored as the card is played. Example: Sky Splitter is a spell that costs [8] and says in part “This spell's Energy cost is reduced by the highest Might among units you control.” Lux, Illuminated is a unit that says “When you play a spell that costs 5 or more, give me +3 [M] this turn.” If a player who controls Lux plays Sky Splitter, Lux’s ability will trigger, regardless of how much was actually paid for Sky Splitter. Example: Defy is a spell which reads “Counter a spell that costs no more than [4] and no more than [A].” Rocket Barrage is a spell that costs [4][C] and has a Repeat cost of [4][C]. Rocket Barrage is a legal target for Defy even if Rocket Barrage’s Repeat cost is paid, because Defy only checks the printed or copied cost of its target. Example: Atakhan is a unit that reads in part “You may kill a friendly unit as an additional cost to play me. If you do, I cost [1] less for each Energy it costs and [Y] less for each Power it costs.” If a player plays Atakhan and chooses to kill a Reflection token that is currently a copy of Noxus Hopeful, Atakhan will cost [4] less.
206.1.: Effects that need to determine an ability’s cost for any purpose use its base cost, ignoring any alterations to that base cost unless otherwise specified. Example: A card reads “When you play an activated ability with Energy cost [7] or more, you may exhaust me to ready up to 2 runes.” A gear has an activated ability that reads “[12], Banish this: Choose an opponent. Banish all units they control. This ability costs [1] less for each point the chosen opponent has.” The ability of the first card will trigger when the activated ability is played, even if the chosen opponent has 6 or more points. Example: An equipment has an ability that reads “Equip [4][A]. This ability costs [1] less for each occupied enemy battlefield.” If its controller plays a unit with Weaponmaster, the Weaponmaster trigger will refer to the cost including the alterations. This is because Weaponmaster specifies that it includes modifications to the cost.