Aluren + Unsubstantiate + Lutri, the Spellchaser

Aluren

Unsubstantiate

Lutri, the Spellchaser

How it works

1. Cast Unsubstantiate by paying its mana cost.
2. Holding priority, cast Lutri without paying its mana cost due to Aluren.
3. When Lutri enters, it triggers, copying Unsubstantiate.
4. Resolve the Unsubstantiate copy, returning Lutri from the battlefield to your hand.
5. Repeat from step 2.