Tanazir Quandrix

Flying, trample
When Tanazir Quandrix enters, double the number of +1/+1 counters on target creature you control.
Whenever Tanazir Quandrix attacks, you may have the base power and toughness of other creatures you control become equal to Tanazir Quandrix's power and toughness until end of turn.

Notion Thief

Flash
If an opponent would draw a card except the first one they draw in each of their draw steps, instead that player skips that draw and you draw a card.

Nighthowler

Bestow {2}{B}{B} (If you cast this card for its bestow cost, it's an Aura spell with enchant creature. It becomes a creature again if it's not attached.)
This creature and enchanted creature each get +X/+X, where X is the number of creature cards in all graveyards.

Exquisite Blood

Whenever an opponent loses life, you gain that much life.

Invigorating Surge

Put a +1/+1 counter on target creature you control, then double the number of +1/+1 counters on that creature.

Bontu's Monument

Black creature spells you cast cost {1} less to cast.
Whenever you cast a creature spell, each opponent loses 1 life and you gain 1 life.

Goblin War Drums

Creatures you control have menace. (They can't be blocked except by two or more creatures.)

Reaper King

({2/W} can be paid with any two mana or with {W}. This card's mana value is 10.)
Other Scarecrow creatures you control get +1/+1.
Whenever another Scarecrow you control enters, destroy target permanent.

K'rrik, Son of Yawgmoth

({B/P} can be paid with either {B} or 2 life.)
Lifelink
For each {B} in a cost, you may pay 2 life rather than pay that mana.
Whenever you cast a black spell, put a +1/+1 counter on K'rrik.