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) ({E} magic symbol) ({E} magic symbol) , sacrificing a creature with mana value 3 or less, and returning Chthonian Nightmare from the battlefield to your hand, returning Skullwinder from your graveyard to the battlefield.
When Skullwinder enters the battlefield, it triggers, returning Walk the Aeons from your graveyard to your hand.
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 at most ({E} magic symbol) ({E} magic symbol) ({E} magic symbol) , sacrificing Skullwinder, and returning Chthonian Nightmare from the battlefield to your hand, returning a creature with mana value 3 or less from your graveyard to the battlefield.