Pack Rat

Pack Rat's power and toughness are each equal to the number of Rats you control.
{2}{B}, Discard a card: Create a token that's a copy of this creature.

Adorable Kitten

When this creature enters, roll a six-sided die. You gain life equal to the result.

Krark's Other Thumb

If you would roll a die, instead roll two of those dice and ignore one of those results.

Tangled Colony

This creature can't block.
When this creature dies, create X 1/1 black Rat creature tokens with "This token can't block," where X is the amount of damage dealt to it this turn.

The Grand Calcutron

When The Grand Calcutron enters, each player's hand becomes a program (an ordered row of revealed cards).
Players can play only the first card of their program.
If a card would be put into a player's hand from anywhere, that player reveals it and places it anywhere within their program instead.
At the beginning of each player's end step, if that player's program has fewer than five cards, they draw cards equal to the difference.
The Grand Calcutron can be your commander.

Relentless Rats

This creature gets +1/+1 for each other creature on the battlefield named Relentless Rats.
A deck can have any number of cards named Relentless Rats.

Voracious Vermin

When this creature enters, create a 1/1 black Rat creature token with "This token can't block."
Whenever another creature you control dies, put a +1/+1 counter on this creature.

Applied Aeronautics

Whenever you crank this Contraption, until end of turn, target creature gets +1/+0, gains flying, and becomes an artifact in addition to its other types.

Rat Colony

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

Angelic Rocket

Flying
When this creature enters, you may destroy target nonland permanent.

Animate Library

Enchant your library
Enchanted library is an artifact creature on the battlefield with power and toughness each equal to the number of cards in it. It's still a library.
If enchanted library would leave the battlefield, exile this Aura instead.

Amateur Auteur

Sacrifice this creature: Destroy target enchantment.

Ineffable Blessing

As this enchantment enters, choose white-bordered or silver-bordered.
Whenever a creature you control with the chosen border enters, draw a card.

Dr. Julius Jumblemorph

Dr. Julius Jumblemorph is every creature type (even if this card isn't on the battlefield).
Whenever a host you control enters, you may search your library and/or graveyard for a card with augment and combine it with that host. If you search your library this way, shuffle.

Kindslaver

{5}, {T}, Sacrifice Kindslaver: A person outside the game controls target player during that player's next turn. Neither player may advise that person until the end of that turn.

Pestilence Rats

Pestilence Rats's power is equal to the number of other Rats on the battlefield. (For example, as long as there are two other Rats on the battlefield, Pestilence Rats's power and toughness are 2/3.)

Border Guardian

Whenever you cast a silver-bordered spell, put a +1/+1 counter on this creature.
Whenever you cast a black-bordered spell, this creature can't be blocked this turn.
Whenever you cast a white-bordered spell, this creature gains double strike until end of turn.

Everythingamajig

{2}, {T}: Draw a card. Activate only if you have no cards in hand.
{8}, {T}: You gain 10 life.
{4}, {T}, Sacrifice this artifact: You may put a silver-bordered or acorn permanent card from your hand onto the battlefield.