BargainBargain is a static ability that functions while the spell with bargain is on the stack. “Bargain” means “As an additional cost to cast this spell, you may sacrifice an artifact, enchantment, or token.” Paying a spell’s bargain cost follows the rules for paying additional costs in rules 601.2b and 601.2f–h.
If a spell’s controller declares the intention to pay that spell’s bargain cost, that spell has been “bargained.” See rule 601.2b.
Objects with bargain have additional abilities that specify what happens if they were bargained. These abilities are linked to the bargain ability printed on that object: they can refer only to that specific bargain ability. See rule 607, “Linked Abilities.”
If part of a spell’s ability has its effect only if that spell was bargained and that part of the ability includes any targets, the spell’s controller chooses those targets only if that spell was bargained. Otherwise, the spell is cast as if it did not have those targets. See rule 601.2c. (CR 702.166) (You may
sacrificeTo sacrifice a permanent, its controller moves it from the battlefield directly to its owner’s graveyard. A player can’t sacrifice something that isn’t a permanent, or something that’s a permanent they don’t control. Sacrificing a permanent doesn’t destroy it, so regeneration or other effects that replace destruction can’t affect this action. (CR 701.21) an artifact, enchantment, or token as you
castTo cast a spell is to take it from the zone it’s in (usually the hand), put it on the stack, and pay its costs, so that it will eventually resolve and have its effect. A player may cast a spell if they have priority. See rule 601, “Casting Spells.”
To cast a card is to cast it as a spell. (CR 701.5) this spell.)
Kellan's Lightblades deals 3 damage to target attacking or blocking creature. If this spell was bargained,
destroyThe only ways a permanent can be destroyed are as a result of an effect that uses the word “destroy” or as a result of the state-based actions that check for lethal damage (see rule 704.5g) or damage from a source with deathtouch (see rule 704.5h). If a permanent is put into its owner’s graveyard for any other reason, it hasn’t been “destroyed.”
A regeneration effect replaces a destruction event. See rule 701.19, “Regenerate.” (CR 701.8) that creature instead.