Karumonix, the Rat King

Toxic 1 (Players dealt combat damage by this
creature also get a poison counter.)

Other Rats you control have toxic 1.

When Karumonix enters the battlefield, look at the
top five cards of your library. You may reveal any
number of Rat cards from among them and put the
revealed cards into your hand. Put the rest on the
bottom of your library in a random order.