Skewer the Critics

2019-01-25 A card's spectacle cost is the same no matter how much life your opponents lost or how many opponents lost life.
2019-01-25 Damage dealt to a player causes that player to lose that much life.
2019-01-25 In a multiplayer game, if an opponent loses life and later that turn leaves the game, you can cast a spell for its spectacle cost. (If a player leaves the game during their turn, that turn continues without an active player.)
2019-01-25 Spectacle doesn't change when you can cast the card. For example, you can't cast a sorcery with spectacle during an opponent's turn unless another effect allows you to do so, even if that player has lost life this turn.
2019-01-25 To determine the total cost of a spell, start with the mana cost or alternative cost you're paying (such as a spectacle cost), add any cost increases, then apply any cost reductions. The converted mana cost of the spell remains unchanged, no matter what the total cost to cast it was.

Card is in preconstructed decks:

mtg.wtf