Snibbles, the Rat King

Rats you control get +1/+1 for each Rat you
control.
Whenever a Rat enters the battlefield under
your control, you may search your library for
a Rat creature card, reveal it, put it into your
hand, then shuffle your library.
{t}, Sacrifice X Rats: Each opponent loses X
life. You gain life equal to the total amount
of life lost this way.