Lazav's first ability triggers, causing you to exile Walk the Aeons from your graveyard and create a Clue artifact token.
Move to your postcombat main phase.
Activate the Clue token by paying ({2} magic symbol) and sacrificing it.
Lazav's second ability triggers, causing it to become a copy of Nightveil Specter until end of turn.
Resolve the Clue ability, causing you to draw a card.
Cast Walk the Aeons from exile by paying ({4} magic symbol) ({U} magic symbol) ({U} magic symbol) due to Lazav's ability, causing you to take an extra turn after this one.