Thalia and The Gitrog Monster

First strike, deathtouch
You may play an additional land on each of your turns.
Creatures and nonbasic lands your opponents control enter the battlefield tapped.
Whenever Thalia and The Gitrog Monster attacks, sacrifice a creature or land, then draw a card.

Mesmeric Fiend

When Mesmeric Fiend enters the battlefield, target opponent reveals their hand and you choose a nonland card from it. Exile that card.
When Mesmeric Fiend leaves the battlefield, return the exiled card to its owner's hand.

Nils, Discipline Enforcer

At the beginning of your end step, for each player, put a +1/+1 counter on up to one target creature that player controls.
Each creature with one or more counters on it can't attack you or planeswalkers you control unless its controller pays {X}, where X is the number of counters on that creature.

Loyal Guardian

Trample
Lieutenant — At the beginning of combat on your turn, if you control your commander, put a +1/+1 counter on each creature you control.

Etchings of the Chosen

As Etchings of the Chosen enters the battlefield, choose a creature type.
Creatures you control of the chosen type get +1/+1.
{1}, Sacrifice a creature of the chosen type: Target creature you control gains indestructible until end of turn. (Damage and effects that say "destroy" don't destroy it.)

Door of Destinies

As Door of Destinies enters the battlefield, choose a creature type.
Whenever you cast a spell of the chosen type, put a charge counter on Door of Destinies.
Creatures you control of the chosen type get +1/+1 for each charge counter on Door of Destinies.

Doom Weaver

Reach
Soulbond (You may pair this creature with another unpaired creature when either enters the battlefield. They remain paired for as long as you control both of them.)
As long as Doom Weaver is paired with another creature, each of those creatures has "When this creature dies, draw cards equal to its power."

And They Shall Know No Fear

Choose a creature type. Creatures you control of the chosen type get +1/+0 and gain indestructible until end of turn.

Vashta Nerada

Indestructible
Shadow (This creature can block or be blocked by only creatures with shadow.)
Morbid — At the beginning of each end step, if a creature died this turn, put a +1/+1 counter on Vashta Nerada.

First-Sphere Gargantua

When First-Sphere Gargantua enters the battlefield, you draw a card and you lose 1 life.
Unearth {2}{B} ({2}{B}: Return this card from your graveyard to the battlefield. It gains haste. Exile it at the beginning of the next end step or if it would leave the battlefield. Unearth only as a sorcery.)

Hunted Horror

Trample
When Hunted Horror enters the battlefield, target opponent creates two 3/3 green Centaur creature tokens with protection from black.

Wretched Bonemass

Wretched Bonemass's power and toughness are each equal to the total power of the exiled cards used to craft it.
Wretched Bonemass has flying as long as an exiled card used to craft it has flying. The same is true for first strike, double strike, deathtouch, haste, hexproof, indestructible, lifelink, menace, protection, reach, trample, and vigilance.

Altar of the Wretched

When Altar of the Wretched enters the battlefield, you may sacrifice a nontoken creature. If you do, draw X cards, then mill X cards, where X is that creature's power.
Craft with one or more creatures {2}{B}{B}
{2}{B}: Return Altar of the Wretched from your graveyard to your hand.

Altar of the Wretched // Wretched Bonemass

Master Biomancer

Each other creature you control enters the battlefield with a number of additional +1/+1 counters on it equal to Master Biomancer's power and as a Mutant in addition to its other types.

Experimental Augury

Look at the top three cards of your library. Put one of them into your hand and the rest on the bottom of your library in any order. Proliferate. (Choose any number of permanents and/or players, then give each another counter of each kind already there.)

Faceless Butcher

When Faceless Butcher enters the battlefield, exile another target creature.
When Faceless Butcher leaves the battlefield, return the exiled card to the battlefield under its owner's control.

Brushland

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

Farseek

Search your library for a Plains, Island, Swamp, or Mountain card, put it onto the battlefield tapped, then shuffle.

For the Ancestors

Choose a creature type. Look at the top six cards of your library. You may reveal any number of cards of the chosen type from among them and put the revealed cards into your hand. Put the rest on the bottom of your library in a random order.
Flashback {3}{G} (You may cast this card from your graveyard for its flashback cost. Then exile it.)

Chasm Skulker

Whenever you draw a card, put a +1/+1 counter on Chasm Skulker.
When Chasm Skulker dies, create X 1/1 blue Squid creature tokens with islandwalk, where X is the number of +1/+1 counters on Chasm Skulker. (They can't be blocked as long as defending player controls an Island.)

Uchuulon

Uchuulon's power is equal to the number of Crabs, Oozes, and/or Horrors you control.
Horrific Symbiosis — At the beginning of your end step, exile up to one target creature card from an opponent's graveyard. If you do, create a token that's a copy of Uchuulon.

Bloodspore Thrinax

Devour 1 (As this enters the battlefield, you may sacrifice any number of creatures. This creature enters the battlefield with that many +1/+1 counters on it.)
Each other creature you control enters the battlefield with an additional X +1/+1 counters on it, where X is the number of +1/+1 counters on Bloodspore Thrinax.

Yavimaya Coast

{T}: Add {C}.
{T}: Add {G} or {U}. Yavimaya Coast deals 1 damage to you.

Grell Philosopher

Aberrant Tinkering — When Grell Philosopher enters the battlefield and at the beginning of your upkeep, each Horror you control gains all activated abilities of target artifact an opponent controls until end of turn. You may spend blue mana as though it were mana of any color to activate those abilities.

Psychosis Crawler

Psychosis Crawler's power and toughness are each equal to the number of cards in your hand.
Whenever you draw a card, each opponent loses 1 life.

Command Tower

{T}: Add one mana of any color in your commander's color identity.

Sméagol, Helpful Guide

At the beginning of your end step, if a creature died under your control this turn, the Ring tempts you.
Whenever the Ring tempts you, target opponent reveals cards from the top of their library until they reveal a land card. Put that card onto the battlefield tapped under your control and the rest into their graveyard.

Bojuka Bog

Bojuka Bog enters the battlefield tapped.
When Bojuka Bog enters the battlefield, exile target player's graveyard.
{T}: Add {B}.

Ardenvale Fealty

Create a 2/2 white Knight creature token with vigilance. (Then exile this card. You may cast the enchantment later from exile.)

Virtue of Loyalty

At the beginning of your end step, put a +1/+1 counter on each creature you control. Untap those creatures.

Virtue of Loyalty // Ardenvale Fealty

Phyrexian Obliterator

Trample
Whenever a source deals damage to Phyrexian Obliterator, that source's controller sacrifices that many permanents.

Nighthowler

Bestow {2}{B}{B} (If you cast this card for its bestow cost, it's an Aura spell with enchant creature. It becomes a creature again if it's not attached to a creature.)
Nighthowler and enchanted creature each get +X/+X, where X is the number of creature cards in all graveyards.

Thrummingbird

Flying
Whenever Thrummingbird deals combat damage to a player, proliferate. (Choose any number of permanents and/or players, then give each another counter of each kind already there.)

Captain N'ghathrod

Horrors you control have menace.
Whenever a Horror you control deals combat damage to a player, that player mills that many cards.
At the beginning of your end step, choose target artifact or creature card in an opponent's graveyard that was put there from their library this turn. Put it onto the battlefield under your control.

Mondrak, Glory Dominus

If one or more tokens would be created under your control, twice that many of those tokens are created instead.
{1}{W/P}{W/P}, Sacrifice two other artifacts and/or creatures: Put an indestructible counter on Mondrak, Glory Dominus. ({W/P} can be paid with either {W} or 2 life.)

Sludge Monster

Whenever Sludge Monster enters the battlefield or attacks, put a slime counter on up to one other target creature.
Non-Horror creatures with slime counters on them lose all abilities and have base power and toughness 2/2.

Intellect Devourer

Devour Intellect — When Intellect Devourer enters the battlefield, each opponent exiles a card from their hand until Intellect Devourer leaves the battlefield.
Body Thief — You may play lands and cast spells from among cards exiled with Intellect Devourer. If you cast a spell this way, you may spend mana as though it were mana of any color to cast it.

Gleancrawler

({B/G} can be paid with either {B} or {G}.)
Trample
At the beginning of your end step, return to your hand all creature cards in your graveyard that were put there from the battlefield this turn.

Llanowar Wastes

{T}: Add {C}.
{T}: Add {B} or {G}. Llanowar Wastes deals 1 damage to you.

Island

Arvinox, the Mind Flail

Arvinox, the Mind Flail isn't a creature unless you control three or more permanents you don't own.
At the beginning of your end step, exile the bottom card of each opponent's library face down. For as long as those cards remain exiled, you may look at them, you may cast permanent spells from among them, and you may spend mana as though it were mana of any color to cast those spells.

Beast Whisperer

Whenever you cast a creature spell, draw a card.

Metallic Mimic

As Metallic Mimic enters the battlefield, choose a creature type.
Metallic Mimic is the chosen type in addition to its other types.
Each other creature you control of the chosen type enters the battlefield with an additional +1/+1 counter on it.

Deathbonnet Hulk

At the beginning of your upkeep, you may exile a card from a graveyard. If a creature card was exiled this way, put a +1/+1 counter on Deathbonnet Hulk.

Deathbonnet Sprout

At the beginning of your upkeep, mill a card. Then if there are three or more creature cards in your graveyard, transform Deathbonnet Sprout. (To mill a card, put the top card of your library into your graveyard.)

Deathbonnet Sprout // Deathbonnet Hulk

The Gitrog Monster

Deathtouch
At the beginning of your upkeep, sacrifice The Gitrog Monster unless you sacrifice a land.
You may play an additional land on each of your turns.
Whenever one or more land cards are put into your graveyard from anywhere, draw a card.

Guardian Project

Whenever a nontoken creature enters the battlefield under your control, if it doesn't have the same name as another creature you control or a creature card in your graveyard, draw a card.

Yarok's Fenlurker

When Yarok's Fenlurker enters the battlefield, each opponent exiles a card from their hand.
{2}{B}: Yarok's Fenlurker gets +1/+1 until end of turn.

Birds of Paradise

Arcane Signet

Creakwood Liege

Other black creatures you control get +1/+1.
Other green creatures you control get +1/+1.
At the beginning of your upkeep, you may create a 1/1 black and green Worm creature token.

Exotic Orchard

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

Gulping Scraptrap

When Gulping Scraptrap enters the battlefield or dies, proliferate. (Choose any number of permanents and/or players, then give each another counter of each kind already there.)

Umbris, Fear Manifest

Umbris, Fear Manifest gets +1/+1 for each card your opponents own in exile.
Whenever Umbris or another Nightmare or Horror enters the battlefield under your control, target opponent exiles cards from the top of their library until they exile a land card.

Seaside Citadel

Seaside Citadel enters the battlefield tapped.
{T}: Add {G}, {W}, or {U}.

Skaab Ruinator

As an additional cost to cast this spell, exile three creature cards from your graveyard.
Flying
You may cast Skaab Ruinator from your graveyard.

From the Rubble

As From the Rubble enters the battlefield, choose a creature type.
At the beginning of your end step, return target creature card of the chosen type from your graveyard to the battlefield with a finality counter on it. (If a creature with a finality counter on it would die, exile it instead.)

Plague Spitter

At the beginning of your upkeep, Plague Spitter deals 1 damage to each creature and each player.
When Plague Spitter dies, it deals 1 damage to each creature and each player.

Aboleth Spawn

Flash
Ward {2}
Probing Telepathy — Whenever a creature entering the battlefield under an opponent's control causes a triggered ability of that creature to trigger, you may copy that ability. You may choose new targets for the copy.

Felidar Retreat

Landfall — Whenever a land enters the battlefield under your control, choose one —
• Create a 2/2 white Cat Beast creature token.
• Put a +1/+1 counter on each creature you control. Those creatures gain vigilance until end of turn.

Raise the Palisade

Choose a creature type. Return all creatures that aren't of the chosen type to their owners' hands.

Brokers Ascendancy

At the beginning of your end step, put a +1/+1 counter on each creature you control and a loyalty counter on each planeswalker you control.

Zellix, Sanity Flayer

Hive Mind — Whenever a player mills one or more creature cards, you create a 1/1 black Horror creature token.
{1}, {T}: Target player mills three cards.
Choose a Background (You can have a Background as a second commander.)

Pact of the Serpent

Choose a creature type. Target player draws X cards and loses X life, where X is the number of creatures they control of the chosen type.

Ulvenwald Abomination

Ulvenwald Captive

Defender
{T}: Add {G}.
{5}{G}{G}: Transform Ulvenwald Captive.

Ulvenwald Captive // Ulvenwald Abomination

Abomination of Gudul

Flying
Whenever Abomination of Gudul deals combat damage to a player, you may draw a card. If you do, discard a card.
Morph {2}{B}{G}{U} (You may cast this card face down as a 2/2 creature for {3}. Turn it face up any time for its morph cost.)

Urza's Incubator

As Urza's Incubator enters the battlefield, choose a creature type.
Creature spells of the chosen type cost {2} less to cast.

Starving Revenant

When Starving Revenant enters the battlefield, surveil 2. Then for each card you put on top of your library, you draw a card and you lose 3 life.
Descend 8 — Whenever you draw a card, if there are eight or more permanent cards in your graveyard, target opponent loses 1 life and you gain 1 life.

Cavern of Souls

As Cavern of Souls enters the battlefield, choose a creature type.
{T}: Add {C}.
{T}: Add one mana of any color. Spend this mana only to cast a creature spell of the chosen type, and that spell can't be countered.

Kindred Discovery

As Kindred Discovery enters the battlefield, choose a creature type.
Whenever a creature you control of the chosen type enters the battlefield or attacks, draw a card.

Gavony Township

{T}: Add {C}.
{2}{G}{W}, {T}: Put a +1/+1 counter on each creature you control.

Grime Gorger

Menace
Whenever Grime Gorger attacks, exile up to one card of each card type from defending player's graveyard. Put a +1/+1 counter on Grime Gorger for each card exiled this way.

Lost in the Maze

Flash
When Lost in the Maze enters the battlefield, tap X target creatures. Put a stun counter on each of those creatures you don't control. (If a permanent with a stun counter would become untapped, remove one from it instead.)
Tapped creatures you control have hexproof.

Phyrexian Swarmlord

Infect (This creature deals damage to creatures in the form of -1/-1 counters and to players in the form of poison counters.)
At the beginning of your upkeep, create a 1/1 green Phyrexian Insect creature token with infect for each poison counter your opponents have.

Shadrix Silverquill

Flying, double strike
At the beginning of combat on your turn, you may choose two. Each mode must target a different player.
• Target player creates a 2/1 white and black Inkling creature token with flying.
• Target player draws a card and loses 1 life.
• Target player puts a +1/+1 counter on each creature they control.

Brainstealer Dragon

Flying
At the beginning of your end step, exile the top card of each opponent's library. You may play those cards for as long as they remain exiled. If you cast a spell this way, you may spend mana as though it were mana of any color to cast it.
Whenever a nonland permanent an opponent owns enters the battlefield under your control, they lose life equal to its mana value.

Kodama's Reach

Search your library for up to two basic land cards, reveal those cards, put one onto the battlefield tapped and the other into your hand, then shuffle.

Master Chef

Commander creatures you own have "This creature enters the battlefield with an additional +1/+1 counter on it" and "Other creatures you control enter the battlefield with an additional +1/+1 counter on them."

Tribute to the World Tree

Whenever a creature enters the battlefield under your control, draw a card if its power is 3 or greater. Otherwise, put two +1/+1 counters on it.

Heroic Intervention

Permanents you control gain hexproof and indestructible until end of turn.

Vanquisher's Banner

As Vanquisher's Banner enters the battlefield, choose a creature type.
Creatures you control of the chosen type get +1/+1.
Whenever you cast a creature spell of the chosen type, draw a card.

Foul Emissary

When Foul Emissary enters the battlefield, look at the top four cards of your library. You may reveal a creature card from among them and put it into your hand. Put the rest on the bottom of your library in any order.
When you sacrifice Foul Emissary while casting a spell with emerge, create a 3/2 colorless Eldrazi Horror creature token.

Froghemoth

Trample, haste
Whenever Froghemoth deals combat damage to a player, exile up to that many target cards from their graveyard. Put a +1/+1 counter on Froghemoth for each creature card exiled this way. You gain 1 life for each noncreature card exiled this way.

Plant Tadpoles

Tap X target creatures. They don't untap during their controllers' next untap steps. (Then exile this card. You may cast the creature later from exile.)

Illithid Harvester

Ceremorphosis — When Illithid Harvester enters the battlefield, turn any number of target tapped nontoken creatures face down. They're 2/2 Horror creatures.

Illithid Harvester // Plant Tadpoles

Kindred Dominance

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

Yarok, the Desecrated

Deathtouch, lifelink
If a permanent entering the battlefield causes a triggered ability of a permanent you control to trigger, that ability triggers an additional time.

Fume Spitter

Sacrifice Fume Spitter: Put a -1/-1 counter on target creature.

Woe Strider

When Woe Strider enters the battlefield, create a 0/1 white Goat creature token.
Sacrifice another creature: Scry 1.
Escape—{3}{B}{B}, Exile four other cards from your graveyard. (You may cast this card from your graveyard for its escape cost.)
Woe Strider escapes with two +1/+1 counters on it.

Toxrill, the Corrosive

At the beginning of each end step, put a slime counter on each creature you don't control.
Creatures you don't control get -1/-1 for each slime counter on them.
Whenever a creature you don't control with a slime counter on it dies, create a 1/1 black Slug creature token.
{U}{B}, Sacrifice a Slug: Draw a card.

Plains

Phyrexian Vindicator

Flying
If damage would be dealt to Phyrexian Vindicator, prevent that damage. When damage is prevented this way, Phyrexian Vindicator deals that much damage to any other target.

Consuming Aberration

Consuming Aberration's power and toughness are each equal to the number of cards in your opponents' graveyards.
Whenever you cast a spell, each opponent reveals cards from the top of their library until they reveal a land card, then puts those cards into their graveyard.

Sakura-Tribe Elder

Sacrifice Sakura-Tribe Elder: Search your library for a basic land card, put that card onto the battlefield tapped, then shuffle.

Howling Chorus

Creatures with power less than Howling Chorus's power can't block it.
Whenever Howling Chorus deals combat damage to a player, create a 3/2 colorless Eldrazi Horror creature token.

Shrill Howler

Creatures with power less than Shrill Howler's power can't block it.
{5}{G}: Transform Shrill Howler.

Shrill Howler // Howling Chorus

Underground Mortuary

({T}: Add {B} or {G}.)
Underground Mortuary enters the battlefield tapped.
When Underground Mortuary enters the battlefield, surveil 1. (Look at the top card of your library. You may put it into your graveyard.)

Herald's Horn

As Herald's Horn enters the battlefield, choose a creature type.
Creature spells you cast of the chosen type cost {1} less to cast.
At the beginning of your upkeep, look at the top card of your library. If it's a creature card of the chosen type, you may reveal it and put it into your hand.

Have for Dinner

Create a 1/1 white Human creature token and a Food token. (Then exile this card. You may cast the creature later from exile.)