Echoing Return

Return target creature card and all other cards with the same name as that card from your graveyard to your hand.

Convolute

Counter target spell unless its controller pays {4}.

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

Each opponent's maximum hand size is reduced by one.

Rat Colony gets +1/+0 for each other Rat you control.
A deck can have any number of cards named Rat Colony.