Retreat to Coralhelm + Llanowar Scout + Azorius Chancery

Retreat to Coralhelm

Llanowar Scout

Azorius Chancery

How it works

1. Activate Llanowar Scout by tapping it, putting Azorius Chancery from your hand onto the battlefield.
2. When Azorius Chancery enters the battlefield, it and Retreat to Coralhelm trigger.
3. Resolve the Azorius Chancery trigger, returning itself from the battlefield to your hand.
4. Resolve the Retreat to Coralhelm trigger, untapping Llanowar Scout.
5. Repeat.