The Metal Overlord

+2: You may return an artifact you control to your hand. The next time you cast an artifact spell this turn, draw a card.
-2: Ultron deals X damage to target creature or planeswalker, where X is the number of artifacts you control.
-8: Each artifact you control becomes a 5/5 colorless Myr creature with haste in addition to its other types. Untap all artifacts you control.