Bolas's Citadel [War of the Spark]

Set: War of the Spark Type: Legendary Artifact Rarity: Rare Cost: {3}{B}{B}{B} You may look at the top card of your library any time.You may play lands and cast spells from the top of your library. If you cast a spell this way, pay life equal to its mana value rather than pay its mana cost.{T}, Sacrifice ten nonland permanents: Each opponent loses 10 life.