Blightbelly Rat

Toxic 1 (Players dealt combat damage by this creature also get a poison counter.)
When this creature dies, proliferate. (Choose any number of permanents and/or players, then give each another counter of each kind already there.)

Agony Warp

Target creature gets -3/-0 until end of turn.
Target creature gets -0/-3 until end of turn.

Countersquall

Counter target noncreature spell. Its controller loses 2 life.

Drainpipe Vermin

When this creature dies, you may pay {B}. If you do, target player discards a card.

Swamp

Marrow-Gnawer

All Rats have fear.
{T}, Sacrifice a Rat: Create X 1/1 black Rat creature tokens, where X is the number of Rats you control.

Thornbite Staff

Equipped creature has "{2}, {T}: This creature deals 1 damage to any target" and "Whenever a creature dies, untap this creature."
Whenever a Shaman creature enters, you may attach this Equipment to it.
Equip {4}

Island

Psychic Strike

Counter target spell. Its controller mills two cards.

Crypt Rats

{X}: This creature deals X damage to each creature and each player. Spend only black mana on X.

Deathmask Nezumi

As long as you have seven or more cards in hand, this creature gets +2/+1 and has fear. (It can't be blocked except by artifact creatures and/or black creatures.)