Prerequisites
- Isochron Scepter on the battlefield
- Energy Arc in exile
- Karn's Touch in hand
- You control creatures that can tap to produce at least
- available
Steps
- Cast Karn's Touch by paying , targeting Isochron Scepter, causing it to become an artifact creature until end of turn
- Activate creatures you control by tapping those, adding
- Activate Isochron Scepter by paying and tapping it, casting a copy of Energy Arc without paying its mana cost, untapping all creatures
- Repeat from step 2