Possible additions

Hunted Lammasu

Flying
When Hunted Lammasu enters, target opponent creates a 4/4 black Horror creature token.

Plan on cutting

Spectral Rider

Intimidate (This creature can't be blocked except by artifact creatures and/or creatures that share a color with it.)

Have

Plains

Drown in Ichor

Target creature gets -4/-4 until end of turn. Proliferate. (Choose any number of permanents and/or players, then give each another counter of each kind already there.)

Arcbound Condor

Flying
Modular 3 (This creature enters with three +1/+1 counters on it. When it dies, you may put its +1/+1 counters on target artifact creature.)
Whenever another artifact you control enters, target creature an opponent controls gets -1/-1 until end of turn.

Grave Pact

Whenever a creature you control dies, each other player sacrifices a creature.

Bilious Skulldweller

Deathtouch
Toxic 1 (Players dealt combat damage by this creature also get a poison counter.)

Blind Obedience

Extort (Whenever you cast a spell, you may pay {W/B}. If you do, each opponent loses 1 life and you gain that much life.)
Artifacts and creatures your opponents control enter tapped.

Tallyman of Nurgle

Lifelink
The Seven-fold Chant — At the beginning of your end step, if a creature died this turn, you draw a card and you lose 1 life. If seven or more creatures died this turn, instead you draw seven cards and you lose 7 life.

Cruel Celebrant

Whenever Cruel Celebrant or another creature or planeswalker you control dies, each opponent loses 1 life and you gain 1 life.

Nimraiser Paladin

Toxic 2 (Players dealt combat damage by this creature also get two poison counters.)
When Nimraiser Paladin enters, return target creature card with mana value 3 or less from your graveyard to your hand.

Ruthless Lawbringer

When Ruthless Lawbringer enters, you may sacrifice another creature. When you do, destroy target nonland permanent.

Haystack

{2}, {T}: Target creature you control phases out. (Treat it and anything attached to it as though they don't exist until your next turn.)

Barracks of the Thousand

(Transforms from Thousand Moons Smithy.)
{T}: Add {W}.
Whenever you cast an artifact or creature spell using mana produced by Barracks of the Thousand, create a white Gnome Soldier artifact creature token with "This creature's power and toughness are each equal to the number of artifacts and/or creatures you control."

Thousand Moons Smithy

When Thousand Moons Smithy enters, create a white Gnome Soldier artifact creature token with "This creature's power and toughness are each equal to the number of artifacts and/or creatures you control."
At the beginning of your first main phase, you may tap five untapped artifacts and/or creatures you control. If you do, transform Thousand Moons Smithy.

Thousand Moons Smithy // Barracks of the Thousand

Caretaker's Talent

(Gain the next level as a sorcery to add its ability.)
Whenever one or more tokens you control enter, draw a card. This ability triggers only once each turn.
{W}: Level 2
When this Class becomes level 2, create a token that's a copy of target token you control.
{3}{W}: Level 3
Creature tokens you control get +2/+2.

The Argent Etchings

(As this Saga enters and after your draw step, add a lore counter.)
I — Incubate 2 five times, then transform all Incubator tokens you control.
II — Creatures you control get +1/+1 and gain double strike until end of turn.
III — Destroy all other permanents except for artifacts, lands, and Phyrexians. Exile The Argent Etchings, then return it to the battlefield (front face up).

Elesh Norn

Vigilance
Whenever a source an opponent controls deals damage to you or a permanent you control, that source's controller loses 2 life unless they pay {1}.
{2}{W}, Sacrifice three other creatures: Exile Elesh Norn, then return it to the battlefield transformed under its owner's control. Activate only as a sorcery.

Elesh Norn // The Argent Etchings

Fierce Retribution

Cleave {5}{W} (You may cast this spell for its cleave cost. If you do, remove the words in square brackets.)
Destroy target [attacking] creature.

Blightbelly Rat

Toxic 1 (Players dealt combat damage by this creature also get a poison counter.)
When Blightbelly Rat dies, proliferate. (Choose any number of permanents and/or players, then give each another counter of each kind already there.)

MacCready, Lamplight Mayor

Whenever a creature you control with power 2 or less attacks, it gains skulk until end of turn. (It can't be blocked by creatures with greater power.)
Whenever a creature with power 4 or greater attacks you, its controller loses 2 life and you gain 2 life.

Serra Ascendant

Lifelink (Damage dealt by this creature also causes you to gain that much life.)
As long as you have 30 or more life, Serra Ascendant gets +5/+5 and has flying.

Caves of Koilos

{T}: Add {C}.
{T}: Add {W} or {B}. Caves of Koilos deals 1 damage to you.

Shadowy Backstreet

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

Thriving Heath

Thriving Heath enters tapped. As it enters, choose a color other than white.
{T}: Add {W} or one mana of the chosen color.

Delney, Streetwise Lookout

Creatures you control with power 2 or less can't be blocked by creatures with power 3 or greater.
If an ability of a creature you control with power 2 or less triggers, that ability triggers an additional time.

Expel the Interlopers

Choose a number between 0 and 10. Destroy all creatures with power greater than or equal to the chosen number.

Jackdaw Savior

Flying
Whenever Jackdaw Savior or another creature you control with flying dies, return another target creature card with lesser mana value from your graveyard to the battlefield.

Elesh Norn, Grand Cenobite

Vigilance
Other creatures you control get +2/+2.
Creatures your opponents control get -2/-2.

Flare of Fortitude

You may sacrifice a nontoken white creature rather than pay this spell's mana cost.
Until end of turn, your life total can't change, and permanents you control gain hexproof and indestructible.

Infectious Inquiry

You draw two cards and you lose 2 life. Each opponent gets a poison counter.

Dune Mover

Toxic 1 (Players dealt combat damage by this creature also get a poison counter.)
When Dune Mover enters, you may search your library for a basic land card, reveal it, then shuffle and put that card on top.

Grafted Butcher

When Grafted Butcher enters, Phyrexians you control gain menace until end of turn.
Other Phyrexians you control get +1/+1.
{3}{B}, Sacrifice an artifact or creature: Return Grafted Butcher from your graveyard to the battlefield. Activate only as a sorcery.

Blazing Archon

Holy Cow

Flash
Flying
When Holy Cow enters, you gain 2 life and scry 1. (Look at the top card of your library. You may put that card on the bottom.)

Holy Mantle

Enchant creature
Enchanted creature gets +2/+2 and has protection from creatures.

Massacre Wurm

When Massacre Wurm enters, creatures your opponents control get -2/-2 until end of turn.
Whenever a creature an opponent controls dies, that player loses 2 life.

Essence of Orthodoxy

Flying
Whenever Essence of Orthodoxy or another Phyrexian you control enters, incubate 2. (Create an Incubator token with two +1/+1 counters on it and "{2}: Transform this artifact." It transforms into a 0/0 Phyrexian artifact creature.)

Guardian of the Great Door

As an additional cost to cast this spell, tap four untapped artifacts, creatures, and/or lands you control.
Flying

Forlorn Flats

Forlorn Flats enters tapped.
When Forlorn Flats enters, it deals 1 damage to target opponent.
{T}: Add {W} or {B}.

Ria Ivor, Bane of Bladehold

Battle cry (Whenever this creature attacks, each other attacking creature gets +1/+0 until end of turn.)
At the beginning of combat on your turn, the next time target creature would deal combat damage to one or more players this combat, prevent that damage. If damage is prevented this way, create that many 1/1 colorless Phyrexian Mite artifact creature tokens with toxic 1 and "This creature can't block."

Tomik, Wielder of Law

Affinity for planeswalkers (This spell costs {1} less to cast for each planeswalker you control.)
Flying, vigilance
Whenever an opponent attacks with creatures, if two or more of those creatures are attacking you and/or planeswalkers you control, that opponent loses 3 life and you draw a card.

Baron Bertram Graywater

Whenever one or more tokens you control enter, create a 1/1 black Vampire Rogue creature token with lifelink. This ability triggers only once each turn.
{1}{B}, Sacrifice another creature or artifact: Draw a card.

Talisman of Hierarchy

{T}: Add {C}.
{T}: Add {W} or {B}. Talisman of Hierarchy deals 1 damage to you.

Kabira Plateau

Kabira Plateau enters tapped.
{T}: Add {W}.

Kabira Takedown

Kabira Takedown deals damage equal to the number of creatures you control to target creature or planeswalker.

Kabira Takedown // Kabira Plateau

Castle Ardenvale

Castle Ardenvale enters tapped unless you control a Plains.
{T}: Add {W}.
{2}{W}{W}, {T}: Create a 1/1 white Human creature token.

Command Tower

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

Skrelv's Hive

At the beginning of your upkeep, you lose 1 life and create a 1/1 colorless Phyrexian Mite artifact creature token with toxic 1 and "This creature can't block."
Corrupted — As long as an opponent has three or more poison counters, creatures you control with toxic have lifelink.

Nadier's Nightblade

Whenever a token you control leaves the battlefield, each opponent loses 1 life and you gain 1 life.

Contagion Engine

When Contagion Engine enters, put a -1/-1 counter on each creature target player controls.
{4}, {T}: Proliferate twice. (Choose any number of permanents and/or players, then give each another counter of each kind already there. Then do it again.)

Firemane Commando

Flying
Whenever you attack with two or more creatures, draw a card.
Whenever another player attacks with two or more creatures, they draw a card if none of those creatures attacked you.

Orzhov Guildgate

Orzhov Guildgate enters tapped.
{T}: Add {W} or {B}.

Crystal Grotto

When Crystal Grotto enters, scry 1.
{T}: Add {C}.
{1}, {T}: Add one mana of any color.

Welcoming Vampire

Flying
Whenever one or more other creatures you control with power 2 or less enter, draw a card. This ability triggers only once each turn.

Mentor of the Meek

Whenever another creature you control with power 2 or less enters, you may pay {1}. If you do, draw a card.

Getting

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.)

Myr Convert

Toxic 1 (Players dealt combat damage by this creature also get a poison counter.)
{T}, Pay 2 life: Add one mana of any color.

Anointed Procession

If an effect would create one or more tokens under your control, it creates twice that many of those tokens instead.

Liliana's Reaver

Deathtouch
Whenever Liliana's Reaver deals combat damage to a player, that player discards a card and you create a tapped 2/2 black Zombie creature token.

Company Commander

Command Section — When Company Commander enters, create a number of 1/1 white Soldier creature tokens equal to the number of opponents you have.
Bring it Down! — Whenever Company Commander attacks, creatures you control gain deathtouch until end of turn.

Necrogen Communion

Enchant creature you control
Enchanted creature has toxic 2. (Players dealt combat damage by it also get two poison counters.)
When enchanted creature dies, return that card to the battlefield under your control.

Metastatic Evangel

Whenever another nontoken creature you control enters, proliferate. (Choose any number of permanents and/or players, then give each another counter of each kind already there.)

Brimaz, Blight of Oreskos

Whenever you cast a Phyrexian creature or artifact creature spell, incubate X, where X is that spell's mana value. (Create an Incubator token with X +1/+1 counters on it and "{2}: Transform this artifact." It transforms into a 0/0 Phyrexian artifact creature.)
At the beginning of each end step, if a Phyrexian died under your control this turn, proliferate.

Wispdrinker Vampire

Flying
Whenever another creature you control with power 2 or less enters, each opponent loses 1 life and you gain 1 life.
{5}{W}{B}: Creatures you control with power 2 or less gain deathtouch and lifelink until end of turn.

Tainted Field

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

Requisition Raid

Spree (Choose one or more additional costs.)
+ {1} — Destroy target artifact.
+ {1} — Destroy target enchantment.
+ {1} — Put a +1/+1 counter on each creature target player controls.

Barren Moor

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

Seraph of the Masses

Convoke (Your creatures can help cast this spell. Each creature you tap while casting this spell pays for {1} or one mana of that creature's color.)
Flying
Seraph of the Masses's power and toughness are each equal to the number of creatures you control.

Escape Tunnel

{T}, Sacrifice Escape Tunnel: Search your library for a basic land card, put it onto the battlefield tapped, then shuffle.
{T}, Sacrifice Escape Tunnel: Target creature with power 2 or less can't be blocked this turn.

Thalisse, Reverent Medium

At the beginning of each end step, create X 1/1 white Spirit creature tokens with flying, where X is the number of tokens you created this turn.

Orim's Chant

Kicker {W} (You may pay an additional {W} as you cast this spell.)
Target player can't cast spells this turn. If this spell was kicked, creatures can't attack this turn.

Orzhov Basilica

Orzhov Basilica enters tapped.
When Orzhov Basilica enters, return a land you control to its owner's hand.
{T}: Add {W}{B}.

Stroke of Midnight

Destroy target nonland permanent. Its controller creates a 1/1 white Human creature token.

Suture Priest

Whenever another creature you control enters, you may gain 1 life.
Whenever a creature an opponent controls enters, you may have that player lose 1 life.

Mirkwood Bats

Flying
Whenever you create or sacrifice a token, each opponent loses 1 life.

By Invitation Only

Choose a number between 0 and 13. Each player sacrifices that many creatures.

Devouring Light

Convoke (Your creatures can help cast this spell. Each creature you tap while casting this spell pays for {1} or one mana of that creature's color.)
Exile target attacking or blocking creature.

Exorcise

Exile target artifact, enchantment, or creature with power 4 or greater.

Kambal, Profiteering Mayor

Whenever one or more tokens your opponents control enter, for each of them, create a tapped token that's a copy of it. This ability triggers only once each turn.
Whenever one or more tokens you control enter, each opponent loses 1 life and you gain 1 life.

Season of the Burrow

Choose up to five {P} worth of modes. You may choose the same mode more than once.
{P} — Create a 1/1 white Rabbit creature token.
{P}{P} — Exile target nonland permanent. Its controller draws a card.
{P}{P}{P} — Return target permanent card with mana value 3 or less from your graveyard to the battlefield with an indestructible counter on it.

Batwing Brume

Prevent all combat damage that would be dealt this turn if {W} was spent to cast this spell. Each player loses 1 life for each attacking creature they control if {B} was spent to cast this spell. (Do both if {W}{B} was spent.)

White Sun's Twilight

You gain X life. Create X 1/1 colorless Phyrexian Mite artifact creature tokens with toxic 1 and "This creature can't block." If X is 5 or more, destroy all other creatures. (Players dealt combat damage by a creature with toxic 1 also get a poison counter.)

Vault of the Archangel

{T}: Add {C}.
{2}{W}{B}, {T}: Creatures you control gain deathtouch and lifelink until end of turn.

Slaughter the Strong

Each player chooses any number of creatures they control with total power 4 or less, then sacrifices all other creatures they control.

Archetype of Finality

Creatures you control have deathtouch.
Creatures your opponents control lose deathtouch and can't have or gain deathtouch.

Phyrexian Fleshgorger

Prototype {1}{B}{B} — 3/3 (You may cast this spell with different mana cost, color, and size. It keeps its abilities and types.)
Menace, lifelink
Ward—Pay life equal to Phyrexian Fleshgorger's power.

Infested Fleshcutter

Equipped creature gets +2/+0.
Whenever equipped creature attacks, create a 1/1 colorless Phyrexian Mite artifact creature token with toxic 1 and "This creature can't block." (Players dealt combat damage by it also get a poison counter.)
Equip {2}{W}

Darkstar Augur

Offspring {B} (You may pay an additional {B} as you cast this spell. If you do, when this creature enters, create a 1/1 token copy of it.)
Flying
At the beginning of your upkeep, reveal the top card of your library and put that card into your hand. You lose life equal to its mana value.

Skullclamp

Equipped creature gets +1/-1.
Whenever equipped creature dies, draw two cards.
Equip {1}

Collector's Cage

Hideaway 5 (When this artifact enters, look at the top five cards of your library, exile one face down, then put the rest on the bottom in a random order.)
{1}, {T}: Put a +1/+1 counter on target creature you control. Then if you control three or more creatures with different powers, you may play the exiled card without paying its mana cost.

Hunted Nightmare

Menace
When Hunted Nightmare enters, target opponent puts a deathtouch counter on a creature they control.

Whisper of the Dross

Target creature gets -1/-1 until end of turn. Proliferate. (Choose any number of permanents and/or players, then give each another counter of each kind already there.)

Promising Vein

{T}: Add {C}.
{1}, {T}, Sacrifice Promising Vein: Search your library for a basic land card, put it onto the battlefield tapped, then shuffle.

Orzhov Signet

Vraska's Fall

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

Fell the Mighty

Destroy all creatures with power greater than target creature's power.

Gravelighter

Flying
When Gravelighter enters, draw a card if a creature died this turn. Otherwise, each player sacrifices a creature.

Phyresis Outbreak

Each opponent gets a poison counter. Then each creature your opponents control gets -1/-1 until end of turn for each poison counter its controller has.