MTG Combo: Clock of Omens + Metalwork Colossus + Witch's Oven
Start withWitch's Oven, Clock of Omens , and 6 CMC of other non-creature artifacts. This will make Metalwork Colossus cost 0 to cast. So cast Metalwork Colossus and sacrifice it to Witch's Oven to make two food. Tap the two food with Clock of Omens to untap Witch's Oven. Sacrifice the two food to return Metalwork Colossus to your hand. Repeat.
This doesn't do anything on its own & needs something triggering off the interaction.