Storm the Seedcore

Distribute four +1/+1 counters among up to four target creatures you control. Creatures you control gain vigilance and trample until end of turn.

Argothian Opportunist

When this creature enters, create a tapped Powerstone token. (It's an artifact with "{T}: Add {C}. This mana can't be spent to cast a nonartifact spell.")

Rootwire Amalgam

Prototype {1}{G} — 2/3 (You may cast this spell with different mana cost, color, and size. It keeps its abilities and types.)
{3}{G}{G}, Sacrifice this creature: Create an X/X colorless Golem artifact creature token, where X is three times this creature's power. It gains haste until end of turn. Activate only as a sorcery.

Evolving Wilds

{T}, Sacrifice this land: Search your library for a basic land card, put it onto the battlefield tapped, then shuffle.

Teething Wurmlet

This creature has deathtouch as long as you control three or more artifacts.
Whenever an artifact you control enters, you gain 1 life. If this is the first time this ability has resolved this turn, put a +1/+1 counter on this creature.

Ingenious Smith

When this creature enters, look at the top four cards of your library. You may reveal an artifact card from among them and put it into your hand. Put the rest on the bottom of your library in a random order.
Whenever one or more artifacts you control enter, put a +1/+1 counter on this creature. This ability triggers only once each turn.

Blossoming Sands

This land enters tapped.
When this land enters, you gain 1 life.
{T}: Add {G} or {W}.

Cogworker's Puzzleknot

When this artifact enters, create a 1/1 colorless Servo artifact creature token.
{1}{W}, Sacrifice this artifact: Create a 1/1 colorless Servo artifact creature token.

Leonin Elder

Whenever an artifact enters, you may gain 1 life.

Plains

Mandible Justiciar

Lifelink
Whenever another artifact you control enters, this creature gets +1/+1 until end of turn.

Clay Champion

This creature enters with three +1/+1 counters on it for each {G}{G} spent to cast it.
When this creature enters, choose up to two other target creatures you control. For each {W}{W} spent to cast this creature, put a +1/+1 counter on each of them.

Simian Simulacrum

When this creature enters, put two +1/+1 counters on target creature you control.
Unearth {2}{G}{G} ({2}{G}{G}: 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.)

Yotian Dissident

Whenever an artifact you control enters, put a +1/+1 counter on target creature you control.