Mass of the Deep

When Mass of the Deep enters the battlefield
each opponent sacrifices a creature.
Whenever a creature dies put a +1/+1 counter on
Mass of the Deep. Then you may have Mass of
the Deep become a copy of that creature except
it's a 1/1 Horror and is black in addition to it's
other colors.
The brain is like the ocean, the deeper you go the more
alien things become.