Consider

Bloodline Culling

Choose one —
• Target creature gets -5/-5 until end of turn.
• Creature tokens get -2/-2 until end of turn.

Land

Swarmyard

{T}: Add {C}.
{T}: Regenerate target Insect, Rat, Spider, or Squirrel. (The next time it would be destroyed this turn, instead tap it, remove it from combat, and heal all damage on it.)

Essential

Liliana's Triumph

Each opponent sacrifices a creature of their choice. If you control a Liliana planeswalker, each opponent also discards a card.

Have

Death Rattle

Delve (Each card you exile from your graveyard while casting this spell pays for {1}.)
Destroy target nongreen creature. It can't be regenerated.

Omit?

Witch-king, Bringer of Ruin

Flying
Whenever Witch-king attacks, defending player sacrifices a creature with the least power among creatures they control.

Lash of the Balrog

As an additional cost to cast this spell, sacrifice a creature or pay {4}.
Destroy target creature.

Bident of Thassa

Whenever a creature you control deals combat damage to a player, you may draw a card.
{1}{U}, {T}: Creatures your opponents control attack this turn if able.

Liliana, Dreadhorde General

Whenever a creature you control dies, draw a card.
+1: Create a 2/2 black Zombie creature token.
−4: Each player sacrifices two creatures of their choice.
−9: Each opponent chooses a permanent they control of each permanent type and sacrifices the rest.

Cower in Fear

Creatures your opponents control get -1/-1 until end of turn.

Mask of Avacyn

Equipped creature gets +1/+2 and has hexproof. (It can't be the target of spells or abilities your opponents control.)
Equip {3}

Dimir Charm

Choose one —
• Counter target sorcery spell.
• Destroy target creature with power 2 or less.
• Look at the top three cards of target player's library. Put one back and the rest into that player's graveyard.

Rend Flesh

Don't Have

Vanishing

Enchant creature
{U}{U}: Enchanted creature phases out. (While it's phased out, it's treated as though it doesn't exist. It phases in before its controller untaps during their next untap step.)

Infernal Grasp

Destroy target creature. You lose 2 life.

Diplomatic Immunity

Enchant creature
Shroud (A permanent with shroud can't be the target of spells or abilities.)
Enchanted creature has shroud.

Plaguecrafter

When this creature enters, each player sacrifices a creature or planeswalker of their choice. Each player who can't discards a card.

Whispersilk Cloak

Equipped creature can't be blocked and has shroud. (It can't be the target of spells or abilities.)
Equip {2}

EDHREC

Rapid Hybridization

Destroy target creature. It can't be regenerated. That creature's controller creates a 3/3 green Frog Lizard creature token.

Valley Rotcaller

Menace
Whenever this creature attacks, each opponent loses X life and you gain X life, where X is the number of other Squirrels, Bats, Lizards, and Rats you control.

Gothmog, Morgul Lieutenant

When Gothmog enters, amass Orcs 1. (Put a +1/+1 counter on an Army you control. It's also an Orc. If you don't control an Army, create a 0/0 black Orc Army creature token first.)
Creature tokens you control have deathtouch.

Sol Ring

Typhoid Rats

Deathtouch (Any amount of damage this deals to a creature is enough to destroy it.)

Distant Melody

Choose a creature type. Draw a card for each permanent you control of that type.

Sheoldred's Edict

Choose one —
• Each opponent sacrifices a nontoken creature of their choice.
• Each opponent sacrifices a creature token of their choice.
• Each opponent sacrifices a planeswalker of their choice.

Seize the Secrets

This spell costs {1} less to cast if you've committed a crime this turn. (Targeting opponents, anything they control, and/or cards in their graveyards is a crime.)
Draw two cards.

Midnight Clock

{T}: Add {U}.
{2}{U}: Put an hour counter on this artifact.
At the beginning of each upkeep, put an hour counter on this artifact.
When the twelfth hour counter is put on this artifact, shuffle your hand and graveyard into your library, then draw seven cards. Exile this artifact.

Butcher of Malakir

Flying
Whenever this creature or another creature you control dies, each opponent sacrifices a creature of their choice.

Professor Onyx

Magecraft — Whenever you cast or copy an instant or sorcery spell, each opponent loses 2 life and you gain 2 life.
+1: You lose 1 life. Look at the top three cards of your library. Put one of them into your hand and the rest into your graveyard.
−3: Each opponent sacrifices a creature with the greatest power among creatures that player controls.
−8: Each opponent may discard a card. If they don't, they lose 3 life. Repeat this process six more times.

Negate

Underworld Connections

Enchant land
Enchanted land has "{T}, Pay 1 life: Draw a card."

Isolation Cell

Whenever an opponent casts a creature spell, that player loses 2 life unless they pay {2}.

Swallowing Plague

Swallowing Plague deals X damage to target creature and you gain X life.

Blighted Fen

{T}: Add {C}.
{4}{B}, {T}, Sacrifice this land: Target opponent sacrifices a creature of their choice.

Shadows' Verdict

Exile all creatures and planeswalkers with mana value 3 or less from the battlefield and all creature and planeswalker cards with mana value 3 or less from all graveyards.

Command Beacon

{T}: Add {C}.
{T}, Sacrifice this land: Put your commander into your hand from the command zone.

Blood Artist

Whenever this creature or another creature dies, target player loses 1 life and you gain 1 life.

Lord Skitter, Sewer King

Whenever another Rat you control enters, exile up to one target card from an opponent's graveyard.
At the beginning of combat on your turn, create a 1/1 black Rat creature token with "This token can't block."

Exotic Orchard

{T}: Add one mana of any color that a land an opponent controls could produce.

Island

Campfire

{1}, {T}: You gain 2 life.
{2}, {T}, Exile this artifact: Put all commanders you own from the command zone and from your graveyard into your hand. Then shuffle your graveyard into your library.

Curse of the Swine

Exile X target creatures. For each creature exiled this way, its controller creates a 2/2 green Boar creature token.

Crippling Fear

Choose a creature type. Creatures that aren't of the chosen type get -3/-3 until end of turn.

Vraska's Fall

Each opponent sacrifices a creature or planeswalker of their choice and gets a poison counter.

Kindred Dominance

Choose a creature type. Destroy all creatures that aren't of the chosen type.

Propaganda

Creatures can't attack you unless their controller pays {2} for each creature they control that's attacking you.

Pack Rat

Pack Rat's power and toughness are each equal to the number of Rats you control.
{2}{B}, Discard a card: Create a token that's a copy of this creature.

Fell Mire

As this land enters, you may pay 3 life. If you don't, it enters tapped.
{T}: Add {B}.

Fell the Profane

Fell the Profane // Fell Mire

Desecration Demon

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

Ice Out

Bargain (You may sacrifice an artifact, enchantment, or token as you cast this spell.)
This spell costs {1} less to cast if it's bargained.
Counter target spell.

Ritual of Soot

Destroy all creatures with mana value 3 or less.

Fellwar Stone

Change the Equation

Choose one —
• Counter target spell with mana value 2 or less.
• Counter target red or green spell with mana value 6 or less.

Rat Colony

This creature gets +1/+0 for each other Rat you control.
A deck can have any number of cards named Rat Colony.

Dream Spoilers

Flying
Whenever you cast a spell during an opponent's turn, up to one target creature an opponent controls gets -1/-1 until end of turn.

Kindred Discovery

As this enchantment enters, choose a creature type.
Whenever a creature you control of the chosen type enters or attacks, draw a card.

Languish

All creatures get -4/-4 until end of turn.

Dimir Cluestone

{T}: Add {U} or {B}.
{U}{B}, {T}, Sacrifice this artifact: Draw a card.

Bandit's Haul

Whenever you commit a crime, put a loot counter on this artifact. This ability triggers only once each turn. (Targeting opponents, anything they control, and/or cards in their graveyards is a crime.)
{T}: Add one mana of any color.
{2}, {T}, Remove two loot counters from this artifact: Draw a card.

Phantom Interference

Spree (Choose one or more additional costs.)
+ {3} — Create a 2/2 white Spirit creature token with flying.
+ {1} — Counter target spell unless its controller pays {2}.

Essence Extraction

Essence Extraction deals 3 damage to target creature and you gain 3 life.

Talisman of Dominance

{T}: Add {C}.
{T}: Add {U} or {B}. This artifact deals 1 damage to you.

Swiftfoot Boots

Equipped creature has hexproof and haste. (It can't be the target of spells or abilities your opponents control. It can attack and {T} no matter when it came under your control.)
Equip {1} ({1}: Attach to target creature you control. Equip only as a sorcery.)

Blot Out

Target opponent exiles a creature or planeswalker they control with the greatest mana value among creatures and planeswalkers they control.

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.

Fleshbag Marauder

When this creature enters, each player sacrifices a creature of their choice.

Charcoal Diamond

This artifact enters tapped.
{T}: Add {B}.

Commander's Sphere

{T}: Add one mana of any color in your commander's color identity.
Sacrifice this artifact: Draw a card.

Psychotic Haze

Psychotic Haze deals 1 damage to each creature and each player.
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.)

Hagra Broodpit

Hagra Mauling

This spell costs {1} less to cast if an opponent controls no basic lands.
Destroy target creature.

Hagra Mauling // Hagra Broodpit

Marrow-Gnawer

All Rats have fear.
{T}, Sacrifice a Rat: Create X 1/1 black Rat creature tokens, where X is the number of Rats you control.

Diabolic Edict

Target player sacrifices a creature of their choice.

Tainted Isle

{T}: Add {C}.
{T}: Add {U} or {B}. Activate only if you control a Swamp.

Tragic Slip

Target creature gets -1/-1 until end of turn.
Morbid — That creature gets -13/-13 until end of turn instead if a creature died this turn.

Phyrexian Arena

At the beginning of your upkeep, you draw a card and you lose 1 life.

One Ring to Rule Them All

(As this Saga enters and after your draw step, add a lore counter. Sacrifice after III.)
I — The Ring tempts you, then each player mills cards equal to your Ring-bearer's power.
II — Destroy all nonlegendary creatures.
III — Each opponent loses 1 life for each creature card in that player's graveyard.

Merciless Executioner

Sunken Hollow

({T}: Add {U} or {B}.)
This land enters tapped unless you control two or more basic lands.

Toxic Deluge

As an additional cost to cast this spell, pay X life.
All creatures get -X/-X until end of turn.

Rooftop Assassin

Flash
Flying, lifelink
When this creature enters, destroy target creature an opponent controls that was dealt damage this turn.

Murderous Cut

Delve (Each card you exile from your graveyard while casting this spell pays for {1}.)
Destroy target creature.

Fetid Imp

Flying
{B}: This creature gains deathtouch until end of turn. (Any amount of damage it deals to a creature is enough to destroy it.)

Baleful Strix

Flying, deathtouch
When this creature enters, draw a card.

Disfigure

Target creature gets -2/-2 until end of turn.

Dockside Chef

{1}{B}, Sacrifice an artifact or creature: Draw a card.

Oath of Liliana

When Oath of Liliana enters, each opponent sacrifices a creature of their choice.
At the beginning of each end step, if a planeswalker entered the battlefield under your control this turn, create a 2/2 black Zombie creature token.

Claim the Precious

Destroy target creature. The Ring tempts you.

Underground River

{T}: Add {C}.
{T}: Add {U} or {B}. This land deals 1 damage to you.

Make an Example

Each opponent separates the creatures they control into two piles. For each opponent, you choose one of their piles. Each opponent sacrifices the creatures in their chosen pile. (Piles can be empty.)

Dimir Signet

Bone Shards

As an additional cost to cast this spell, sacrifice a creature or discard a card.
Destroy target creature or planeswalker.

Extract a Confession

As an additional cost to cast this spell, you may collect evidence 6. (Exile cards with total mana value 6 or greater from your graveyard.)
Each opponent sacrifices a creature of their choice. If evidence was collected, instead each opponent sacrifices a creature with the greatest power among creatures they control.

Thought Vessel

You have no maximum hand size.
{T}: Add {C}.

Drag to the Bottom

Domain — Each creature gets -X/-X until end of turn, where X is 1 plus the number of basic land types among lands you control.

Unholy Indenture

Enchant creature
When enchanted creature dies, return that card to the battlefield under your control with a +1/+1 counter on it.

Lightning Greaves

Equipped creature has haste and shroud. (It can't be the target of spells or abilities.)
Equip {0}

Ringsight

The Ring tempts you. Search your library for a card that shares a color with a legendary creature you control, reveal it, put it into your hand, then shuffle.

Oppression

Whenever a player casts a spell, that player discards a card.

Rush of Dread

Spree (Choose one or more additional costs.)
+ {1} — Target opponent sacrifices half the creatures they control of their choice, rounded up.
+ {2} — Target opponent discards half the cards in their hand, rounded up.
+ {2} — Target opponent loses half their life, rounded up.

Smallpox

Each player loses 1 life, discards a card, sacrifices a creature of their choice, then sacrifices a land of their choice.