Curse of the Cabal

Target player sacrifices half the permanents they control, rounded down.
Suspend 2—{2}{B}{B} (Rather than cast this card from your hand, you may pay {2}{B}{B} and exile it with two time counters on it. At the beginning of your upkeep, remove a time counter. When the last is removed, you may cast it without paying its mana cost.)
At the beginning of each player's upkeep, if Curse of the Cabal is suspended, that player may sacrifice a permanent. If the player does, put two time counters on Curse of the Cabal.

Sin Prodder

Menace
At the beginning of your upkeep, reveal the top card of your library. Any opponent may have you put that card into your graveyard. If a player does, Sin Prodder deals damage to that player equal to that card's mana value. Otherwise, put that card into your hand.

Carrion Wurm

Whenever Carrion Wurm attacks or blocks, any player may exile three cards from their graveyard. If a player does, Carrion Wurm assigns no combat damage this turn.

Shakedown Heavy

Menace
Whenever Shakedown Heavy attacks, defending player may have you draw a card. If they do, untap Shakedown Heavy and remove it from combat.

Dash Hopes

When you cast this spell, any player may pay 5 life. If a player does, counter Dash Hopes.
Counter target spell.

Risk Factor

Target opponent may have Risk Factor deal 4 damage to them. If that player doesn't, you draw three cards.
Jump-start (You may cast this card from your graveyard by discarding a card in addition to paying its other costs. Then exile this card.)

Zerapa Minotaur

First strike
{2}: Zerapa Minotaur loses first strike until end of turn. Any player may activate this ability.

Brain Gorgers

When you cast this spell, any player may sacrifice a creature. If a player does, counter Brain Gorgers.
Madness {1}{B} (If you discard this card, discard it into exile. When you do, cast it for its madness cost or put it into your graveyard.)

Longhorn Firebeast

When Longhorn Firebeast enters the battlefield, any opponent may have it deal 5 damage to them. If a player does, sacrifice Longhorn Firebeast.

Infinite Hourglass

At the beginning of your upkeep, put a time counter on Infinite Hourglass.
All creatures get +1/+0 for each time counter on Infinite Hourglass.
{3}: Remove a time counter from Infinite Hourglass. Any player may activate this ability but only during any upkeep step.

Clackbridge Troll

Trample, haste
When Clackbridge Troll enters the battlefield, target opponent creates three 0/1 white Goat creature tokens.
At the beginning of combat on your turn, any opponent may sacrifice a creature. If a player does, tap Clackbridge Troll, you gain 3 life, and you draw a card.

Book Burning

Any player may have Book Burning deal 6 damage to them. If no one does, target player mills six cards.

Ribbon Snake

Flying
{2}: Ribbon Snake loses flying until end of turn. Any player may activate this ability.

Browbeat

Any player may have Browbeat deal 5 damage to them. If no one does, target player draws three cards.

Reservoir Kraken

Trample, ward {2}
At the beginning of each combat, if Reservoir Kraken is untapped, any opponent may tap an untapped creature they control. If they do, tap Reservoir Kraken and create a 1/1 blue Fish creature token with "This creature can't be blocked."

Breaking Point

Any player may have Breaking Point deal 6 damage to them. If no one does, destroy all creatures. Creatures destroyed this way can't be regenerated.

Argothian Wurm

Trample
When Argothian Wurm enters the battlefield, any player may sacrifice a land. If a player does, put Argothian Wurm on top of its owner's library.

Vexing Devil

When Vexing Devil enters the battlefield, any opponent may have it deal 4 damage to them. If a player does, sacrifice Vexing Devil.

Phantasmagorian

When you cast this spell, any player may discard three cards. If a player does, counter Phantasmagorian.
Discard three cards: Return Phantasmagorian from your graveyard to your hand.

Distant Memories

Search your library for a card, exile it, then shuffle. Any opponent may have you put that card into your hand. If no player does, you draw three cards.

Temporal Extortion

When you cast this spell, any player may pay half their life, rounded up. If a player does, counter Temporal Extortion.
Take an extra turn after this one.

Sivriss, Nightmare Speaker

{T}, Sacrifice another creature or an artifact: For each opponent, you mill a card, then return that card from your graveyard to your hand unless that player pays 3 life. (To mill a card, put the top card of your library into your graveyard.)
Choose a Background (You can have a Background as a second commander.)

Prowling Pangolin

When Prowling Pangolin enters the battlefield, any player may sacrifice two creatures. If a player does, sacrifice Prowling Pangolin.

Worms of the Earth

Players can't play lands.
Lands can't enter the battlefield.
At the beginning of each upkeep, any player may sacrifice two lands or have Worms of the Earth deal 5 damage to that player. If a player does either, destroy Worms of the Earth.

Carrion Rats

Whenever Carrion Rats attacks or blocks, any player may exile a card from their graveyard. If a player does, Carrion Rats assigns no combat damage this turn.

Gravestorm

At the beginning of your upkeep, target opponent may exile a card from their graveyard. If that player doesn't, you may draw a card.

Desecration Demon

Flying
At the beginning of each combat, any opponent may sacrifice a creature. If a player does, tap Desecration Demon and put a +1/+1 counter on it.