Isochron Scepter + Energy Arc + Xenic Poltergeist

Isochron Scepter

Energy Arc

Xenic Poltergeist

How it works

1. Activate Xenic Poltergeist's first ability by paying 1 and tapping it, causing Isochron Scepter to become an artifact creature until your next upkeep.
2. Activate creatures you control by tapping those, adding 3.
3. Activate Isochron Scepter by paying 2 and tapping it, casting a copy of Energy Arc without paying its mana cost, untapping all creatures.
4. Repeat from step 2.