Karn, Legacy Reforged, Karn, Silver Golem, Lithoform Engine, and Voltaic Construct

Prerequisites

• Karn, Legacy Reforged on the battlefield
• Karn, Silver Golem on the battlefield
• Lithoform Engine on the battlefield
• Voltaic Construct on the battlefield
• Lithoform Engine does not have summoning sickness
• You control at least one additional artifact
• available

Steps

1. At the beginning of your upkeep, Karn, Legacy Reforged triggers
2. Holding priority, activate Karn, Silver Golem by paying , causing Lithoform Engine to become an artifact creature until end of turn
3. Activate Lithoform Engine's first ability by paying and tapping it, copying Karn, Legacy Reforged's ability
4. Resolve the copy of Karn, Legacy Reforged's ability, adding for each artifact you control that cannot be spent to cast nonartifact spells
5. Activate Voltaic Construct by paying , untapping Lithoform Engine
6. Repeat from step 3

Results

• Infinite colorless mana that cannot be spent to cast nonartifact spells
• Infinite untap of artifact creatures you control