Isochron Scepter + Elder Druid + Energy Arc

Isochron Scepter

Elder Druid

Energy Arc

How it works

1. Activate any number of creatures you control by tapping them, adding at least 5.
2. Activate Isochron Scepter by paying 2 and tapping it, casting a copy of Energy Arc without paying its mana cost.
3. Resolve Energy Arc, untapping all creatures you control.
4. Activate Elder Druid by paying 3 and tapping it, untapping Isochron Scepter.
5. Repeat.

This clever engine lets you generate infinite mana and untaps by turning a single Isochron Scepter into a repeatable source of Energy Arc. Because Energy Arc untaps all of your creatures upon resolution, your mana-producing creatures can be repeatedly tapped for fuel. To keep the loop going, Elder Druid uses its ability to untap the Isochron Scepter, perfectly setting the stage for the next iteration.