Master of Etherium is a rare Artifact Creature — Vedalken Wizard card from Duel Decks: Elspeth vs. Tezzeret (DDF), collector number 48. Current market price: $0.58, TCGplayer market prices via Scryfall.
Master of Etherium's power and toughness are each equal to the number of artifacts you control. Other artifact creatures you control get +1/+1.