Retreat to Coralhelm + Ghost Town + Skyshroud Ranger

Retreat to Coralhelm

Ghost Town

Skyshroud Ranger

How it works

1. During any opponent's turn, activate Skyshroud Ranger by tapping it, putting Ghost Town from your hand onto the battlefield.
2. When Ghost Town enters the battlefield, Retreat to Coralhelm triggers, untapping Skyshroud Ranger.
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.