Alien Onslaught

Cumulative upkeep {p/b} (At the beginning of your upkeep, put an age counter on this permanent, then sacrifice it unless you pay its upkeep cost for each age counter on it. {p/b} can be paid with either {b} or 2 life.)
Whenever you pay Alien Onslaught's cumulative upkeep, you may create X 1/1 black Outrider creature tokens with haste, where X is the number of age counters on Alien Onslaught.