Etch-King Highmore

Etch-King Highmore costs {1} less for each
card you own you've exiled this turn.
The first time you cascade each turn, you
may exile cards until you exile a card with
the same mana value or 1 more instead.
(A cascade of mana value 3 would cause you
to reveal until you reveal a card that costs 4
mana or less.)