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.

Swamp

Infernal Contract

Draw four cards. You lose half your life, rounded up.

Swarm of Rats

Swarm of Rats's power is equal to the number of Rats you control.

Sever Soul

Destroy target nonblack creature. It can't be regenerated. You gain life equal to its toughness.

Nezumi Cutthroat

Fear (This creature can't be blocked except by artifact creatures and/or black creatures.)
This creature can't block.

Dirge of Dread

All creatures gain fear until end of turn. (They can't be blocked except by artifact creatures and/or black creatures.)
Cycling {1}{B} ({1}{B}, Discard this card: Draw a card.)
When you cycle this card, you may have target creature gain fear until end of turn.

Chittering Rats

When this creature enters, target opponent puts a card from their hand on top of their library.

Salvat 2005