Saren, Scheming Spectre

+1: Create a colorless artifact token named Etherium Cell with "{t}, Sacrifice this artifact: Add one mana of any color."
-2: Target creature gets +X/-X until end of turn, where X is the number of artifacts you control.
-7: Emblem: "At the beginning of combat on your turn, target artifact you control becomes an artifact creature with base power and toughness 5/5."