Dreadhorde Butcher

Haste
Whenever Dreadhorde Butcher deals combat damage to a player or planeswalker, put a +1/+1 counter on Dreadhorde Butcher.
When Dreadhorde Butcher dies, it deals damage equal to its power to any target.

Sun Titan

Vigilance
Whenever Sun Titan enters or attacks, you may return target permanent card with mana value 3 or less from your graveyard to the battlefield.

Judith, the Scourge Diva

Other creatures you control get +1/+0.
Whenever a nontoken creature you control dies, Judith, the Scourge Diva deals 1 damage to any target.

Gray Merchant of Asphodel

When Gray Merchant of Asphodel enters, each opponent loses X life, where X is your devotion to black. You gain life equal to the life lost this way. (Each {B} in the mana costs of permanents you control counts toward your devotion to black.)

Agent of Masks

At the beginning of your upkeep, each opponent loses 1 life. You gain life equal to the life lost this way.

Oros, the Avenger

Flying
Whenever Oros, the Avenger deals combat damage to a player, you may pay {2}{W}. If you do, Oros deals 3 damage to each nonwhite creature.

Boltwing Marauder

Flying
Whenever another creature you control enters, target creature gets +2/+0 until end of turn.

Boros Reckoner

Whenever Boros Reckoner is dealt damage, it deals that much damage to any target.
{R/W}: Boros Reckoner gains first strike until end of turn.

Deathbringer Thoctar

Whenever another creature dies, you may put a +1/+1 counter on Deathbringer Thoctar.
Remove a +1/+1 counter from Deathbringer Thoctar: It deals 1 damage to any target.

Cruel Celebrant

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

Ancestor Dragon

Flying
Whenever one or more creatures you control attack, you gain 1 life for each attacking creature.

Siege-Gang Commander

When Siege-Gang Commander enters, create three 1/1 red Goblin creature tokens.
{1}{R}, Sacrifice a Goblin: Siege-Gang Commander deals 2 damage to any target.

Teysa Karlov

If a creature dying causes a triggered ability of a permanent you control to trigger, that ability triggers an additional time.
Creature tokens you control have vigilance and lifelink.

Falkenrath Aristocrat

Flying, haste
Sacrifice a creature: Falkenrath Aristocrat gains indestructible until end of turn. If the sacrificed creature was a Human, put a +1/+1 counter on Falkenrath Aristocrat.

Sangromancer

Flying
Whenever a creature an opponent controls dies, you may gain 3 life.
Whenever an opponent discards a card, you may gain 3 life.