({1} magic symbol) ({U} magic symbol) available plus enough mana to cast Walk the Aeons and Returned Pastcaller each turn.
Steps
Cast Walk the Aeons by paying its mana cost, causing you to take an extra turn after this one.
Cast Returned Pastcaller by paying its mana cost.
When Returned Pastcaller enters the battlefield, it triggers, returning Walk the Aeons from your graveyard to your hand.
Move to your next turn.
Activate Dour Port-Mage by paying ({1} magic symbol) ({U} magic symbol) and tapping it, returning Returned Pastcaller from the battlefield to your hand.
Dour Port-Mage triggers, causing you to draw a card.