This spell costsless to cast, where X is the total converted mana cost of noncreature artifacts you control.
Sacrifice two artifacts: Return Metalwork Colossus from your graveyard to your hand.
9/20/2016 If a permanent has in its mana cost, X is considered to be 0.
9/20/2016 The total cost to cast Metalwork Colossus is locked in before you pay that cost. For example, if you control three noncreature artifacts each with converted mana cost 2, including one you can sacrifice to add to your mana pool, the total cost of Metalwork Colossus is . Then you can sacrifice the artifact when you activate mana abilities just before paying the cost.
9/20/2016 If the total converted mana cost of noncreature artifacts you control is 11 or greater, Metalwork Colossus costs to cast.
9/20/2016 Once a player has announced that they are casting Metalwork Colossus, no player may take actions to try to change the number of artifacts its controller controls before that spell’s cost is locked in.
9/20/2016 Metalwork Colossus’s last ability can be activated only if it is in your graveyard.