Poison Gym

When another gym enters the battlefield, exile
this with a visited counter on it. When you
control no gyms, if this is in exile with a visited
counter on it, you may put this in your graveyard.
At the beginning of your upkeep distribute X
-1/-1 counters on any number of target creatures,
counters can not exceed that creatures toughness,
where X is half the number of differently named
gyms in exile rounded down.