Activate Ashnod's Altar by sacrificing Wretched Throng, adding CC.
When Wretched Throng dies, it and Pitiless Plunderer trigger.
Holding priority, activate Sundering Archaic by paying 2, putting Wretched Throng from your graveyard onto the bottom of your library.
Resolve the Pitiless Plunderer trigger, creating a Treasure token.
Resolve the Wretched Throng trigger, putting Wretched Throng from your library into your hand.
Activate the Treasure by tapping and sacrificing it, adding .
Cast Wretched Throng by paying due to Heliod
Repeat.
This intricate loop turns a humble common into an infinite engine by feeding Wretched Throng to Ashnod's Altar for colorless mana while simultaneously triggering Pitiless Plunderer to spawn a Treasure token. Sundering Archaic cleverly recycles the Throng from your graveyard straight to the bottom of your library, ensuring the dying creature's own triggered ability can immediately tutor it right back to your hand. Meanwhile, the flash-granting, cost-reducing presence of Heliod, the Radiant Dawn // Heliod, the Warped Eclipse slashes the casting cost of the Throng so that the mana from the Treasure and the Altar smoothly sustains the entire process indefinitely.