Chthonian Nightmare and Shambling Ghast on the battlefield.
You have at least three energy counters.
Steps
Activate Chthonian Nightmare by paying ({E} magic symbol) ({E} magic symbol) ({E} magic symbol) , sacrificing Shambling Ghast and returning Chthonian Nightmare from the battlefield to your hand.
When Shambling Ghast dies, it triggers, creating a Treasure token.
Resolve the Chthonian Nightmare ability, returning Priest of Gix from your graveyard to the battlefield.
When Priest of Gix enters the battlefield, it triggers, adding ({B} magic symbol) ({B} magic symbol) ({B} magic symbol) .
Activate the Treasure by tapping and sacrificing it, adding ({1} magic symbol) .
When Chthonian Nightmare enters the battlefield, it triggers, causing you to get ({E} magic symbol) ({E} magic symbol) ({E} magic symbol) .
Activate Chthonian Nightmare by paying ({E} magic symbol) , sacrificing Priest of Gix and returning Chthonian Nightmare from the battlefield to your hand, returning Shambling Ghast from your graveyard to the battlefield.