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 Rootwire Amalgam: Create an X/X colorless Golem artifact creature token, where X is three times Rootwire Amalgam's power. It gains haste until end of turn. Activate only as a sorcery.

Arcane Proxy

Prototype {1}{U}{U} — 2/1 (You may cast this spell with different mana cost, color, and size. It keeps its abilities and types.)
When Arcane Proxy enters, if you cast it, exile target instant or sorcery card with mana value less than or equal to Arcane Proxy's power from your graveyard. Copy that card. You may cast the copy without paying its mana cost.

Artificer Class

(Gain the next level as a sorcery to add its ability.)
The first artifact spell you cast each turn costs {1} less to cast.
{1}{U}: Level 2
When this Class becomes level 2, reveal cards from the top of your library until you reveal an artifact card. Put that card into your hand and the rest on the bottom of your library in a random order.
{5}{U}: Level 3
At the beginning of your end step, create a token that's a copy of target artifact you control.

Clay Champion

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

Etherium Sculptor

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

Wurmcoil Engine

Deathtouch, lifelink
When Wurmcoil Engine dies, create a 3/3 colorless Phyrexian Wurm artifact creature token with deathtouch and a 3/3 colorless Phyrexian Wurm artifact creature token with lifelink.

Blightsteel Colossus

Trample, infect, indestructible
If Blightsteel Colossus would be put into a graveyard from anywhere, reveal Blightsteel Colossus and shuffle it into its owner's library instead.

Padeem, Consul of Innovation

Artifacts you control have hexproof.
At the beginning of your upkeep, if you control the artifact with the highest mana value or tied for the highest mana value, draw a card.