Retreat to Coralhelm + Llanowar Scout + Rakdos Carnarium

Retreat to Coralhelm

Llanowar Scout

Rakdos Carnarium

How it works

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