Ancestral Sandstorm

Whenever a creature enters the battlefield under
your control, put a +1/+1 counter on each
creature you control.
Whenever a creature enters the battlefield under
an opponents control, put a -1/-1 counter on
each creature that player controls.
"Despite being in no danger, I cannot help but tremble
when I witness the ancestors unleash their full fury on
our enemies." -Anafenza