Bolas's Citadel [Promo Pack: Theros Beyond Death]

Description

Set:	Promo Pack: Theros Beyond Death
Type:	Legendary Artifact
Rarity:	Rare
Cost:	null

You may look at the top card of your library any time.
You may play the top card of your library. If you cast a spell this way, pay life equal to its converted mana cost rather than pay its mana cost.
T, Sacrifice ten nonland permanents: Each opponent loses 10 life.