Spike Feeder

Spike Feeder enters with two +1/+1 counters on it.
{2}, Remove a +1/+1 counter from Spike Feeder: Put a +1/+1 counter on target creature.
Remove a +1/+1 counter from Spike Feeder: You gain 2 life.

Parallel Lives

If an effect would create one or more tokens under your control, it creates twice that many of those tokens instead.

Epicure of Blood

Whenever you gain life, each opponent loses 1 life.

Exquisite Blood

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

Mindcrank

Whenever an opponent loses life, that player mills that many cards. (Damage causes loss of life.)

Power Word Kill

Destroy target non-Angel, non-Demon, non-Devil, non-Dragon creature.

Grave Pact

Whenever a creature you control dies, each other player sacrifices a creature of their choice.

Gravecrawler

Gravecrawler can't block.
You may cast Gravecrawler from your graveyard as long as you control a Zombie.

Dictate of Erebos

Flash
Whenever a creature you control dies, each opponent sacrifices a creature of their choice.

Zulaport Cutthroat

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

Lisette, Dean of the Root

Whenever you gain life, you may pay {1}. If you do, put a +1/+1 counter on each creature you control and those creatures gain trample until end of turn.

Valentin, Dean of the Vein

Menace, lifelink
If a nontoken creature an opponent controls would die, exile it instead. When you do, you may pay {2}. If you do, create a 1/1 black and green Pest creature token with "When this creature dies, you gain 1 life."

Valentin, Dean of the Vein // Lisette, Dean of the Root

Bloodchief Ascension

At the beginning of each end step, if an opponent lost 2 or more life this turn, you may put a quest counter on Bloodchief Ascension. (Damage causes loss of life.)
Whenever a card is put into an opponent's graveyard from anywhere, if Bloodchief Ascension has three or more quest counters on it, you may have that player lose 2 life. If you do, you gain 2 life.

Skullclamp

Equipped creature gets +1/-1.
Whenever equipped creature dies, draw two cards.
Equip {1}

Blood Artist

Whenever Blood Artist or another creature dies, target player loses 1 life and you gain 1 life.