Culling the Weak

As an additional cost to cast this spell, sacrifice a creature.
Add {B}{B}{B}{B}.

Dead Ringers

Destroy two target nonblack creatures unless either one is a color the other isn't. They can't be regenerated.

Faerie Macabre

Flying
Discard this card: Exile up to two target cards from graveyards.

King's Assassin

{T}: Destroy target tapped creature. Activate only during your turn, before attackers are declared.

Leyline of the Void

If this card is in your opening hand, you may begin the game with it on the battlefield.
If a card would be put into an opponent's graveyard from anywhere, exile it instead.

Mutilate

All creatures get -1/-1 until end of turn for each Swamp you control.

Treasure

Pitiless Plunderer

Whenever another creature you control dies, create a Treasure token. (It's an artifact with "{T}, Sacrifice this token: Add one mana of any color.")

Rat Colony

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

Stitcher's Supplier

When this creature enters or dies, mill three cards. (Put the top three cards of your library into your graveyard.)

Street Wraith

Swampwalk (This creature can't be blocked as long as defending player controls a Swamp.)
Cycling—Pay 2 life. (Pay 2 life, Discard this card: Draw a card.)

Cathar Commando

Flash
{1}, Sacrifice this creature: Destroy target artifact or enchantment.

Tendrils of Agony

Target player loses 2 life and you gain 2 life.
Storm (When you cast this spell, copy it for each spell cast before it this turn. You may choose new targets for the copies.)

Wishclaw Talisman

This artifact enters with three wish counters on it.
{1}, {T}, Remove a wish counter from this artifact: Search your library for a card, put it into your hand, then shuffle. An opponent gains control of this artifact. Activate only during your turn.

Worst Fears

You control target player during that player's next turn. Exile Worst Fears. (You see all cards that player could see and make all decisions for them.)

Ancient Grudge

Destroy target artifact.
Flashback {G} (You may cast this card from your graveyard for its flashback cost. Then exile it.)

Blazing Rootwalla

{R}: This creature gets +2/+0 until end of turn. Activate only once each turn.
Madness {0} (If you discard this card, discard it into exile. When you do, cast it for its madness cost or put it into your graveyard.)

Mystery Booster 2