Retreat to Coralhelm + Ghost Town + Llanowar Scout

Retreat to Coralhelm

Ghost Town

Llanowar Scout

How it works

1. During any opponent's turn, activate Llanowar Scout by tapping it, putting Ghost Town from your hand onto the battlefield.
2. When Ghost Town enters the battlefield, Retreat to Coralhelm triggers, untapping Llanowar Scout.
3. Activate Ghost Town's first ability by tapping it, adding C.
4. Activate Ghost Town's second ability by paying 0, returning it from the battlefield to your hand.
5. Repeat.