If a permanent has in its mana cost, X is considered to be 0.

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.

If the total converted mana cost of noncreature artifacts you control is 11 or greater, Metalwork Colossus costs to cast.

Once a player has announced that he or she is 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.

Metalwork Colossus’s last ability can be activated only if it is in your graveyard.