The Gates of Attrition

At the start of each opponent's main phase, they
must choose one of two options: tap at least one
of each type of basic land. This mana goes into
your mana pool until the end of your first main
phase; they must pay CMC of {x} to choose this
option.
—or—
Exile {x} cards from that opponent's deck. You
may play these cards as if they are in your hand.