Cast Notorious Throng for its prowl cost by paying 5, causing you to take an extra turn after this one.
Cast Eternal Witness by paying its mana cost.
When Eternal Witness enters the battlefield, it triggers, returning Notorious Throng from your graveyard to your hand.
Move to your next turn.
Activate Dour Port-Mage by paying 1 and tapping it, returning Eternal Witness from the battlefield to your hand.
Dour Port-Mage triggers, causing you to draw a card.
Repeat.
This elegant loop starts by casting Notorious Throng for its prowl cost, leveraging a successful Rogue attack to swarm the board with Faerie Rogue tokens and earn an extra turn. When you follow up by casting Eternal Witness, its entry trigger reaches into your graveyard to pluck that very same Notorious Throng right back to your hand. To keep the chain unbroken, Dour Port-Mage uses its activated ability to bounce Eternal Witness back to your hand for reuse on the extra turn, all while drawing you an extra card thanks to its passive draw trigger whenever creatures leave without dying.