Seveus, The Iron Work

: Having 0 or less loyalty does not destroy this card as long as you control at least 3 non-land colorless permanents on the battlefield.
+1: Create a 0/1 colorless artifact creature called "Iron Crab". When that card leaves the battlefield, add 1 mana of any color.
-7: Return target non-land permanent from your graveyard with converted mana cost equal to or less than 7.