Chromatic Orrery + Grinning Ignus + Mirage Mirror + Grapeshot + Mirror Gallery

Chromatic Orrery

Grinning Ignus

Mirage Mirror

Grapeshot

Mirror Gallery

How it works

1. Tap Orrery for 5 mana.
2. Tap 2 mana to activate mirror, targeting grinning ignus.
3. In response, activate mirror again targeting orrery.
4. tap mirror for 5 mana before letting it become an ignus.
5. Use one mana to return mirror to your hand using ignus's ability.
6. this adds 3 to your mana pool.
7. 8 floating.
8. cast mirror from your hand, 5 floating.
9. Repeat.
10. Cast grapeshot for Infinite damage.