Menace Creatures you control have wither. (They deal damage to creatures in the form of -1/-1 counters.) Whenever a creature an opponent controls dies, if its toughness was less than 1, draw a card.

When this artifact enters, put a -1/-1 counter on target creature. {4}, {T}: Proliferate. (Choose any number of permanents and/or players, then give each another counter of each kind already there.)

Whenever you put one or more -1/-1 counters on a creature, create that many 1/1 black Insect creature tokens.

Whenever this creature enters or attacks, put a -1/-1 counter on up to one target creature. Creatures your opponents control with -1/-1 counters on them can't block.

Extort (Whenever you cast a spell, you may pay {W/B}. If you do, each opponent loses 1 life and you gain that much life.) Whenever you tap a Swamp for mana, add an additional {B}.

Search your library for a card, then shuffle and put that card on top. You lose 2 life.

Flying, deathtouch Whenever an opponent loses life, you gain that much life. (Damage causes loss of life.)

Wither (This deals damage to creatures in the form of -1/-1 counters.) Whenever a creature an opponent controls with a -1/-1 counter on it dies, you may return that card to the battlefield under your control.

Whenever this creature or another creature you control dies, each opponent loses 1 life and you gain 1 life.

When The Meathook Massacre enters, each creature gets -X/-X until end of turn. Whenever a creature you control dies, each opponent loses 1 life. Whenever a creature an opponent controls dies, you gain 1 life.

Protection from Humans Pay 1 life, Sacrifice another creature: Put a -1/-1 counter on up to one target creature and draw a card. {B}{B}, Discard a card: Proliferate. (Choose any number of permanents and/or players, then give each another counter of each kind already there.)

Haste Whenever a creature an opponent controls dies, put a +1/+1 counter on Yahenni. Sacrifice another creature: Yahenni gains indestructible until end of turn.