A-ファイレクシアの幻(げん)視(し)

At the beginning of your upkeep, exile the top two cards of your library. You may play one of those cards this turn.

At the beginning of your end step, if you didn't play a card from exile this turn, create a tapped Powerstone token. (It's an artifact with ": Add . This mana can't be spent to cast a nonartifact spell.")