Cast Invasion of Arcavios by paying ({3} magic symbol) ({U} magic symbol) ({U} magic symbol) .
When Invasion of Arcavios enters the battlefield, it triggers, returning Walk the Aeons from your graveyard to your hand, or searching your library for Walk the Aeons and putting it into your hand, if needed.
Cast Walk the Aeons by paying ({4} magic symbol) ({U} magic symbol) ({U} magic symbol) .
Brinelin triggers, returning Invasion of Arcavios to your hand from the battlefield.
Resolve Walk the Aeons, causing you to take an extra turn after this one.