Lightning Runner and Aetherwind Basker on the battlefield.
You control at least six creatures.
An opponent cannot block and kill Lightning Runner or Aetherwind Basker.
Aetherwind Basker does not have summoning sickness.
Steps
Declare Lightning Runner and Aetherwind Basker as attackers, triggering their abilities.
Resolve the Aetherwind Basker trigger, causing you to get at least six ({E} magic symbol) .
Resolve the Lightning Runner trigger, causing you to get ({E} magic symbol) ({E} magic symbol) , and then pay eight ({E} magic symbol) to untap all creatures you control and to get an additional combat phase after this one.
Repeat.
If you control more than six creatures, this combo will net infinite ({E} magic symbol) .