Prototype Portal + Gonti's Aether Heart + Voltaic Key + Lithoform Engine

Prototype Portal

Gonti's Aether Heart

Voltaic Key

Lithoform Engine

How it works

1. Activate Prototype Portal by paying 6 and tapping it.
2. In response, activate Lithoform Engine by paying 2 and tapping it, copying Prototype Portal's activated ability.
3. Activate Voltaic Key by paying 1 and tapping it, untapping Lithoform Engine.
4. activate Lithoform Engine by paying 2 and tapping it, copying Prototype Portal's activated ability again.
5. Resolve one Prototype Portal ability, creating a token copy of Gonti's Aether Heart.
6. Gonti's Aether Heart triggers, adding EE.
7. Resolve a second Prototype Portal ability, creating a token copy of Gonti's Aether Heart.
8. Put one of the Gonti's Aether Heart tokens into the graveyard due to the legend rule.
9. Both Gonti's Aether Heart copies trigger, adding a total of EEEE.
10. Resolve the last Prototype Portal ability, creating a token copy of Gonti's Aether Heart.
11. Put one of the Gonti's Aether Heart tokens into the graveyard due to the legend rule.
12. Both Gonti's Aether Heart copies trigger, adding a total of EEEE.
13. Activate the Gonti's Aether Heart token by paying eight E and exiling it, causing you to take an extra turn after this one.
14. Repeat each turn.