Dabrit's Miasma

When Dabrit's Miasma enter the battlefield, if
you control your commander, put a -1/-1
counter on each creature an opponent controls.
Then, Draw X cards and lose X life, where X is
the number of permanents with counters on
them.
Whenever a land enters or leaves the battlefield, proliferate. (Choose any number of permanents
and/or players, then give each another counter of each
kind already there.)