BuybackBuyback appears on some instants and sorceries. It represents two static abilities that function while the spell is on the stack. “Buyback [cost]” means “You may pay an additional [cost] as you cast this spell” and “If the buyback cost was paid, put this spell into its owner’s hand instead of into that player’s graveyard as it resolves.” Paying a spell’s buyback cost follows the rules for paying additional costs in rules 601.2b and 601.2f–h. (CR 702.27)—Pay 4 life. (You may pay 4 life in addition to any other costs 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. If you do, put this card into your hand as it resolves.)
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) target nonblack creature. It can't be regenerated.