Mystic Speculation

Buyback 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.

To “scry N” means to look at the top N cards of your library, then put any number of them on the bottom of your library in any order and the rest on top of your library in any order.

If a player is instructed to scry 0, no scry event occurs. Abilities that trigger whenever a player scries won’t trigger.

If multiple players scry at once, each of those players looks at the top cards of their library at the same time. Those players decide in APNAP order (see rule 101.4) where to put those cards, then those cards move at the same time.

An ability that triggers whenever a player scries triggers after the process described in rule 701.18a is complete, even if some or all of those actions were impossible.