Ancient Den

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.)

Ghostly Prison

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

Furnace Hellkite

Affinity for artifacts (This spell costs {1} less to cast for each artifact you control.)
Flying
{R}: This creature gets +1/+0 until end of turn.

Ripples of Potential

Proliferate, then choose any number of permanents you control that had a counter put on them this way. Those permanents phase out. (To proliferate, choose any number of permanents and/or players, then give each another counter of each kind already there. Treat phased-out permanents and anything attached to them as though they don't exist until their controller's next turn.)

Filigree Vector

When this creature enters, put a +1/+1 counter on each of any number of target creatures and a charge counter on each of any number of target artifacts.
{1}, {T}, Sacrifice another artifact: Proliferate. (Choose any number of permanents and/or players, then give each another counter of each kind already there.)

Inspirit, Flagship Vessel

Station (Tap another creature you control: Put charge counters equal to its power on this Spacecraft. Station only as a sorcery. It's an artifact creature at 8+.)
STATION 1+
At the beginning of combat on your turn, put your choice of a +1/+1 counter or two charge counters on up to one other target artifact.
STATION 8+
Flying
Other artifacts you control have hexproof and indestructible.

Propaganda

Steel Overseer

{T}: Put a +1/+1 counter on each artifact creature you control.

Kilo, Apogee Mind

Haste
Whenever Kilo becomes tapped, proliferate. (Choose any number of permanents and/or players, then give each another counter of each kind already there.)

Patrolling Peacemaker

This creature enters with two +1/+1 counters on it.
Whenever an opponent commits a crime, proliferate. (They commit a crime if they target an opponent, anything an opponent controls, and/or cards in an opponent's graveyard. To proliferate, you choose any number of permanents and/or players, then give each another counter of each kind already there.)

Cryptothrall

Protector — Other artifact creatures you control have hexproof.

Uthros Research Craft

Station (Tap another creature you control: Put charge counters equal to its power on this Spacecraft. Station only as a sorcery. It's an artifact creature at 12+.)
STATION 3+
Whenever you cast an artifact spell, draw a card. Put a charge counter on this Spacecraft.
STATION 12+
Flying
This Spacecraft gets +1/+0 for each artifact you control.

Sami, Wildcat Captain

Double strike, vigilance
Spells you cast have affinity for artifacts. (They cost {1} less to cast for each artifact you control.)

Etherium Sculptor

Artifact spells you cast cost {1} less to cast.

Paradise Mantle

Equipped creature has "{T}: Add one mana of any color."
Equip {1}

Walking Ballista

This creature enters with X +1/+1 counters on it.
{4}: Put a +1/+1 counter on this creature.
Remove a +1/+1 counter from this creature: It deals 1 damage to any target.

Cloud Key

As this artifact enters, choose artifact, creature, enchantment, instant, or sorcery.
Spells you cast of the chosen type cost {1} less to cast.

Reject Imperfection

Counter target spell. If that spell's mana value was 3 or less, proliferate. (Choose any number of permanents and/or players, then give each another counter of each kind already there.)

Pinnacle Emissary

Whenever you cast an artifact spell, create a 1/1 colorless Drone artifact creature token with flying and "This token can block only creatures with flying."
Warp {U/R} (You may cast this card from your hand for its warp cost. Exile this creature at the beginning of the next end step, then you may cast it from exile on a later turn.)

Tekuthal, Inquiry Dominus

Flying
If you would proliferate, proliferate twice instead.
{1}{U/P}{U/P}, Remove three counters from among other artifacts, creatures, and planeswalkers you control: Put an indestructible counter on Tekuthal. ({U/P} can be paid with either {U} or 2 life.)

Skrelv, Defector Mite

Toxic 1 (Players dealt combat damage by this creature also get a poison counter.)
Skrelv can't block.
{W/P}, {T}: Choose a color. Another target creature you control gains toxic 1 and hexproof from that color until end of turn. It can't be blocked by creatures of that color this turn. ({W/P} can be paid with either {W} or 2 life.)

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.)

Foundry Inspector

Enthusiastic Mechanaut

Flying
Artifact spells you cast cost {1} less to cast.

Thought Monitor

Affinity for artifacts (This spell costs {1} less to cast for each artifact you control.)
Flying
When this creature enters, draw two cards.

Surge Conductor

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

Insight Engine

{2}, {T}: Put a charge counter on this artifact, then draw a card for each charge counter on it.

Crystalline Crawler

Converge — This creature enters with a +1/+1 counter on it for each color of mana spent to cast it.
Remove a +1/+1 counter from this creature: Add one mana of any color.
{T}: Put a +1/+1 counter on this creature.

Dreamtide Whale

Vanishing 2 (This creature enters with two time counters on it. At the beginning of your upkeep, remove a time counter from it. When the last is removed, sacrifice it.)
Whenever a player casts their second spell each turn, proliferate. (Choose any number of permanents and/or players, then give each another counter of each kind already there.)

Seat of the Synod

Jhoira, Weatherlight Captain

Whenever you cast a historic spell, draw a card. (Artifacts, legendaries, and Sagas are historic.)

Padeem, Consul of Innovation

Artifacts you control have hexproof. (They can't be the targets of spells or abilities your opponents control.)
At the beginning of your upkeep, if you control the artifact with the greatest mana value or tied for the greatest mana value, draw a card.