Sky Splitter

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.

356.4.e. If a discount applies a minimum cost, that minimum applies only to that discount. Example: Eager Apprentice says "While I'm at a battlefield, the Energy costs for spells you play is reduced by [1], to a minimum of [1]." A player who controls Eager Apprentice and a unit with 7 Might plays Sky Splitter, a spell that costs 8 Energy and says "This spell's Energy cost is reduced by the highest Might among units you control." That player can choose to apply Eager Apprentice's discount first, reducing Sky Splitter's Energy cost to 7, then apply Sky Splitter's discount, reducing its Energy cost to 0. If they applied these discounts in the other order, Sky Splitter's Energy cost would be 1.