Orzhov Ascendancy

{w}{w}{b}{b}: Exile target creature with converted
mana cost 3 or less.
Whenever one or more creatures are exiled by a
source you control, put that many tax counters
on Orzhov Ascendancy.
At the beginning of your upkeep, if there are 15
or more tax counters on Orzhov Ascendancy, you
win the game.