Each player loses a third of their life, then discards a third of the cards in their hand, then sacrifices a third of the creatures they control of their choice, then sacrifices a third of the lands they control of their choice. Round up each time.

Hymn to Tourach

Target player discards two cards at random.

Abyssal Specter

Flying
Whenever this creature deals damage to a player, that player discards a card.

Greed

Swamp

The Wretched

At end of combat, gain control of all creatures blocking this creature for as long as you control this creature.

Word of Command

Look at target opponent's hand and choose a card from it. You control that player until Word of Command finishes resolving. The player plays that card if able. While doing so, the player can activate mana abilities only if they're from lands that player controls and only if mana they produce is spent to activate other mana abilities of lands the player controls and/or to play that card. If the chosen card is cast as a spell, you control the player while that spell is resolving.

Pestilence

At the beginning of the end step, if no creatures are on the battlefield, sacrifice this enchantment.
{B}: This enchantment deals 1 damage to each creature and each player.

Sorceress Queen

{T}: Target creature other than this creature has base power and toughness 0/2 until end of turn.

Knight of Stromgald

Protection from white
{B}: This creature gains first strike until end of turn.
{B}{B}: This creature gets +1/+0 until end of turn.

Oubliette

When this enchantment enters, target creature phases out until this enchantment leaves the battlefield. Tap that creature as it phases in this way. (Auras and Equipment phase out with it. While permanents are phased out, they're treated as though they don't exist.)

Savannah

Tranquility

Animate Dead

Enchant creature card in a graveyard
When this Aura enters, if it's on the battlefield, it loses "enchant creature card in a graveyard" and gains "enchant creature put onto the battlefield with this Aura." Return enchanted creature card to the battlefield under your control and attach this Aura to it. When this Aura leaves the battlefield, that creature's controller sacrifices it.
Enchanted creature gets -1/-0.

Tormod's Crypt

{T}, Sacrifice this artifact: Exile target player's graveyard.

The Rack

As this artifact enters, choose an opponent.
At the beginning of the chosen player's upkeep, this artifact deals X damage to that player, where X is 3 minus the number of cards in their hand.

Drain Life

Spend only black mana on X.
Drain Life deals X damage to any target. You gain life equal to the damage dealt, but not more life than the player's life total before the damage was dealt, the planeswalker's loyalty before the damage was dealt, or the creature's toughness.

Sengir Vampire

Flying (This creature can't be blocked except by creatures with flying or reach.)
Whenever a creature dealt damage by this creature this turn dies, put a +1/+1 counter on this creature.

Jayemdae Tome

Terror

Destroy target nonartifact, nonblack creature. It can't be regenerated.

Mishra's Factory

{T}: Add {C}.
{1}: This land becomes a 2/2 Assembly-Worker artifact creature until end of turn. It's still a land.
{T}: Target Assembly-Worker creature gets +1/+1 until end of turn.

Disenchant

Brushland

{T}: Add {C}.
{T}: Add {G} or {W}. This land deals 1 damage to you.

Nightmare

Flying (This creature can't be blocked except by creatures with flying or reach.)
Nightmare's power and toughness are each equal to the number of Swamps you control.

City of Brass

Whenever this land becomes tapped, it deals 1 damage to you.
{T}: Add one mana of any color.

Will-o'-the-Wisp

Flying (This creature can't be blocked except by creatures with flying or reach.)
{B}: Regenerate this creature. (The next time this creature would be destroyed this turn, instead tap it, remove it from combat, and heal all damage on it.)

Icy Manipulator

{1}, {T}: Tap target artifact, creature, or land.

Dark Ritual

Bayou

Scrubland

Dance of the Dead

Enchant creature card in a graveyard
When this Aura enters, if it's on the battlefield, it loses "enchant creature card in a graveyard" and gains "enchant creature put onto the battlefield with this Aura." Put enchanted creature card onto the battlefield tapped under your control and attach this Aura to it. When this Aura leaves the battlefield, that creature's controller sacrifices it.
Enchanted creature gets +1/+1 and doesn't untap during its controller's untap step.
At the beginning of the upkeep of enchanted creature's controller, that player may pay {1}{B}. If the player does, untap that creature.

Mindstab Thrull

Whenever this creature attacks and isn't blocked, you may sacrifice it. If you do, defending player discards three cards.

Conch Horn

{1}, {T}, Sacrifice this artifact: Draw two cards, then put a card from your hand on top of your library.

Black Vise

As this artifact enters, choose an opponent.
At the beginning of the chosen player's upkeep, this artifact deals X damage to that player, where X is the number of cards in their hand minus 4.