Dreadhound

When Dreadhound enters, mill three cards. (Put the top three cards of your library into your graveyard.)
Whenever a creature dies or a creature card is put into a graveyard from a library, each opponent loses 1 life.

Swamp

The Meathook Massacre

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.

Bloodflow Connoisseur

Sacrifice a creature: Put a +1/+1 counter on Bloodflow Connoisseur.

Blood Tithe

Each opponent loses 3 life. You gain life equal to the life lost this way.

Delina, Wild Mage

Whenever Delina, Wild Mage attacks, choose target creature you control, then roll a d20.
1—14 | Create a tapped and attacking token that's a copy of that creature, except it's not legendary and it has "At end of combat, exile this creature."
15—20 | Create one of those tokens. You may roll again.

Plains

Corpse Knight

Whenever another creature you control enters, each opponent loses 1 life.

Butcher of the Horde

Flying
Sacrifice another creature: Butcher of the Horde gains your choice of vigilance, lifelink, or haste until end of turn.

Cruel Celebrant

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

Barbarian Class

(Gain the next level as a sorcery to add its ability.)
If you would roll one or more dice, instead roll that many dice plus one and ignore the lowest roll.
{1}{R}: Level 2
Whenever you roll one or more dice, target creature you control gets +2/+0 and gains menace until end of turn.
{2}{R}: Level 3
Creatures you control have haste.

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.

Ashnod's Altar

Splinter Twin

Enchant creature
Enchanted creature has "{T}: Create a token that's a copy of this creature, except it has haste. Exile that token at the beginning of the next end step."