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.

Warehouse Tabby

Whenever an enchantment you control is put into a graveyard from the battlefield, create a 1/1 black Rat creature token with "This creature can't block."
{1}{B}: Warehouse Tabby gains deathtouch until end of turn.

Peer into the Abyss

Target player draws cards equal to half the number of cards in their library and loses half their life. Round up each time.

Unholy Citadel

Black legendary creatures you control have "bands with other legendary creatures." (Any legendary creatures can attack in a band as long as at least one has "bands with other legendary creatures." Bands are blocked as a group. If at least two legendary creatures you control, one of which has "bands with other legendary creatures," are blocking or being blocked by the same creature, you divide that creature's combat damage, not its controller, among any of the creatures it's being blocked by or is blocking.)

Pulling Teeth

Clash with an opponent. If you win, target player discards two cards. Otherwise, that player discards a card. (Each clashing player reveals the top card of their library, then puts that card on the top or bottom. A player wins if their card had a higher mana value.)

Peppersmoke

Target creature gets -1/-1 until end of turn. If you control a Faerie, draw a card.

Abomination

Whenever Abomination blocks or becomes blocked by a green or white creature, destroy that creature at end of combat.

Stitch Together

Return target creature card from your graveyard to your hand.
Threshold — Return that card from your graveyard to the battlefield instead if seven or more cards are in your graveyard.

Blowfly Infestation

Whenever a creature dies, if it had a -1/-1 counter on it, put a -1/-1 counter on target creature.

Sacrifice

As an additional cost to cast this spell, sacrifice a creature.
Add an amount of {B} equal to the sacrificed creature's mana value.

Skull Catapult

{1}, {T}, Sacrifice a creature: Skull Catapult deals 2 damage to any target.

Barren Moor

Barren Moor enters tapped.
{T}: Add {B}.
Cycling {B} ({B}, Discard this card: Draw a card.)

Brink of Madness

At the beginning of your upkeep, if you have no cards in hand, sacrifice Brink of Madness and target opponent discards their hand.

Ghosts of the Damned

{T}: Target creature gets -1/-0 until end of turn.

Gnat Miser

Each opponent's maximum hand size is reduced by one.

Ebon Praetor

First strike, trample
At the beginning of your upkeep, put a -2/-2 counter on Ebon Praetor.
Sacrifice a creature: Remove a -2/-2 counter from Ebon Praetor. If the sacrificed creature was a Thrull, put a +1/+0 counter on Ebon Praetor. Activate only during your upkeep and only once each turn.

Dauthi Horror

Shadow (This creature can block or be blocked by only creatures with shadow.)
Dauthi Horror can't be blocked by white creatures.

Castle Locthwain

Castle Locthwain enters tapped unless you control a Swamp.
{T}: Add {B}.
{1}{B}{B}, {T}: Draw a card, then you lose life equal to the number of cards in your hand.

Cabal Coffers

{2}, {T}: Add {B} for each Swamp you control.

Bloodcurdler

Flying
At the beginning of your upkeep, mill a card.
Threshold — As long as seven or more cards are in your graveyard, Bloodcurdler gets +1/+1 and has "At the beginning of your end step, exile two cards from your graveyard."

Gempalm Polluter

Cycling {B}{B} ({B}{B}, Discard this card: Draw a card.)
When you cycle Gempalm Polluter, you may have target player lose life equal to the number of Zombies on the battlefield.

Lingering Death

Enchant creature
At the beginning of the end step of enchanted creature's controller, that player sacrifices that creature.

Old Flitterfang

Flying
At the beginning of each end step, if a creature died this turn, create a Food token. (It's an artifact with "{2}, {T}, Sacrifice this artifact: You gain 3 life.")
{2}{B}, Sacrifice another creature or artifact: Old Flitterfang gets +2/+2 until end of turn.

Chime of Night

Enchant creature
When Chime of Night is put into a graveyard from the battlefield, destroy target nonblack creature.

Flow of Maggots

Cumulative upkeep {1} (At the beginning of your upkeep, put an age counter on this permanent, then sacrifice it unless you pay its upkeep cost for each age counter on it.)
Flow of Maggots can't be blocked by non-Wall creatures.

Horn of Greed

Whenever a player plays a land, that player draws a card.

The Rack

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

Mortuary

Whenever a creature is put into your graveyard from the battlefield, put that card on top of your library.

Necratog

Exile the top creature card of your graveyard: Necratog gets +2/+2 until end of turn.

Myojin of Night's Reach

Myojin of Night's Reach enters with a divinity counter on it if you cast it from your hand.
Myojin of Night's Reach has indestructible as long as it has a divinity counter on it.
Remove a divinity counter from Myojin of Night's Reach: Each opponent discards their hand.

Surging Dementia

Ripple 4 (When you cast this spell, you may reveal the top four cards of your library. You may cast spells with the same name as this spell from among those cards without paying their mana costs. Put the rest on the bottom of your library.)
Target player discards a card.

Cosmic Horror

First strike
At the beginning of your upkeep, destroy Cosmic Horror unless you pay {3}{B}{B}{B}. If Cosmic Horror is destroyed this way, it deals 7 damage to you.

Planar Despair

Domain — All creatures get -1/-1 until end of turn for each basic land type among lands you control.

Shizo, Death's Storehouse

{T}: Add {B}.
{B}, {T}: Target legendary creature gains fear until end of turn. (It can't be blocked except by artifact creatures and/or black creatures.)

Zodiac Rat

Swampwalk (This creature can't be blocked as long as defending player controls a Swamp.)

Pit Imp

Flying
{B}: Pit Imp gets +1/+0 until end of turn. Activate no more than twice each turn.

Boggart Birth Rite

Return target Goblin card from your graveyard to your hand.

Bone Harvest

Put any number of target creature cards from your graveyard on top of your library.
Draw a card at the beginning of the next turn's upkeep.

Snow-Covered Swamp

Seizan, Perverter of Truth

At the beginning of each player's upkeep, that player loses 2 life and draws two cards.

Ice Cauldron

{X}, {T}: You may exile a nonland card from your hand. You may cast that card for as long as it remains exiled. Put a charge counter on Ice Cauldron and note the type and amount of mana spent to pay this activation cost. Activate only if there are no charge counters on Ice Cauldron.
{T}, Remove a charge counter from Ice Cauldron: Add Ice Cauldron's last noted type and amount of mana. Spend this mana only to cast the last card exiled with Ice Cauldron.

Urborg

{T}: Add {B}.
{T}: Target creature loses first strike or swampwalk until end of turn.

Weakstone

Black Vise

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

Arcane Lighthouse

{T}: Add {C}.
{1}, {T}: Until end of turn, creatures your opponents control lose hexproof and shroud and can't have hexproof or shroud.

Spoils of Evil

For each artifact or creature card in target opponent's graveyard, add {C} and you gain 1 life.

Misshapen Fiend

Sickening Shoal

You may exile a black card with mana value X from your hand rather than pay this spell's mana cost.
Target creature gets -X/-X until end of turn.

Arcum's Whistle

{3}, {T}: Choose target non-Wall creature the active player has controlled continuously since the beginning of the turn. That player may pay {X}, where X is that mana value. If they don't pay, the creature attacks this turn if able, and at the beginning of the next end step, destroy it if it didn't attack this turn. Activate only before attackers are declared.

Island of Wak-Wak

{T}: Target creature with flying has base power 0 until end of turn.

Spymaster's Vault

Spymaster's Vault enters tapped unless you control a Swamp.
{T}: Add {B}.
{B}, {T}: Target creature you control connives X, where X is the number of creatures that died this turn. (Draw X cards, then discard X cards. Put a +1/+1 counter on that creature for each nonland card discarded this way.)

Gemstone Caverns

If Gemstone Caverns is in your opening hand and you're not the starting player, you may begin the game with Gemstone Caverns on the battlefield with a luck counter on it. If you do, exile a card from your hand.
{T}: Add {C}. If Gemstone Caverns has a luck counter on it, instead add one mana of any color.

Basal Thrull

Mana Web

Whenever a land an opponent controls is tapped for mana, tap all lands that player controls that could produce any type of mana that land could produce.

Mind Warp

Look at target player's hand and choose X cards from it. That player discards those cards.

Zombie Scavengers

Exile the top creature card of your graveyard: Regenerate Zombie Scavengers.

Barrow Ghoul

At the beginning of your upkeep, sacrifice Barrow Ghoul unless you exile the top creature card of your graveyard.

Odylic Wraith

Swampwalk (This creature can't be blocked as long as defending player controls a Swamp.)
Whenever Odylic Wraith deals damage to a player, that player discards a card.

Evil Eye of Urborg

Non-Eye creatures you control can't attack.
Whenever Evil Eye of Urborg becomes blocked by a creature, destroy that creature.

Hasran Ogress

Whenever Hasran Ogress attacks, it deals 3 damage to you unless you pay {2}.

Everglades

Everglades enters tapped.
When Everglades enters, sacrifice it unless you return an untapped Swamp you control to its owner's hand.
{T}: Add {C}{B}.

Plaguebearer

{X}{X}{B}: Destroy target nonblack creature with mana value X.

Dread Specter

Whenever Dread Specter blocks or becomes blocked by a nonblack creature, destroy that creature at end of combat.

Vampiric Embrace

Enchant creature
Enchanted creature gets +2/+2 and has flying.
Whenever a creature dealt damage by enchanted creature this turn dies, put a +1/+1 counter on that creature.

Feast of Succession

All creatures get -4/-4 until end of turn. You become the monarch.

Priest of Yawgmoth

{T}, Sacrifice an artifact: Add an amount of {B} equal to the sacrificed artifact's mana value.

Grotesque Mutation

Target creature gets +3/+1 and gains lifelink until end of turn. (Damage dealt by the creature also causes its controller to gain that much life.)

Blighted Shaman

{T}, Sacrifice a Swamp: Target creature gets +1/+1 until end of turn.
{T}, Sacrifice a creature: Target creature gets +2/+2 until end of turn.