At the beginning of your combat phase, Mishra triggers.
Holding priority, activate Lithoform Engine's first ability by paying ({2} magic symbol) and tapping it, copying Mishra's trigger.
Resolve the first Mishra trigger, creating a 4/4 artifact creature token copy of Gonti's Aether Heart named Mishra's Warform.
When Mishra's Warform enters the battlefield, it and Gonti's Aether Heart trigger, causing you to get four energy counters.
Resolve the second Mishra trigger from step 1, creating a 4/4 artifact creature token copy of Gonti's Aether Heart named Mishra's Warform.
Put either Mishra's Warform into your graveyard due to the legend rule.
When the second Mishra's Warform enters the battlefield, both Mishra's Warforms and Gonti's Aether Heart trigger, causing you to get six energy counters.
Activate the remaining Mishra's Warform by paying eight energy counters and exiling it, causing you to take an extra turn after this one.