Gandalf the White + Gonti's Aether Heart + Prototype Portal + Lithoform Engine

Gandalf the White

Gonti's Aether Heart

Prototype Portal

Lithoform Engine

How it works

1. Activate Prototype Portal by paying 6 and tapping it.
2. Holding priority, activate Lithoform Engine's first ability by paying 2 and tapping it, copying Prototype Portal's ability.
3. Resolve the copy of Prototype Portal's ability, creating a token copy of Gonti's Aether Heart.
4. When the Gonti's Aether Heart token enters the battlefield, it triggers twice, causing you to get EEEE.
5. Resolve the original Prototype Portal ability, creating a token copy of Gonti's Aether Heart.
6. Put either Gonti's Aether Heart token into your graveyard due to the legend rule.
7. When the Gonti's Aether Heart token enters the battlefield, it triggers twice, causing you to get EEEE.
8. Activate the remaining Gonti's Aether Heart token by paying eight E and exiling it, causing you to take an extra turn after this one.
9. Repeat each turn.