When Flameskull dies, it triggers, exiling it and the top card of your library with the ability to cast one from exile this turn.
Resolve the Viscera Seer ability.
Cast Flameskull from exile by paying 1.
Prosper's second ability triggers, creating two Treasure tokens.
Activate the Treasures by tapping and sacrificing them, adding 2.
Repeat.
This delightful engine hinges on the synergy between Flameskull and Viscera Seer, where you sacrifice the skull to the seer, triggering Flameskull's Rejuvenation to exile itself alongside another card from your library. Because you are casting Flameskull from exile, Prosper, Tome-Bound steps in to generate a Treasure token whenever you play a card from exile. That Treasure generation is doubled by Bard, King of Dale, turning every loop into a windfall of two mana-producing artifacts whose output is supercharged by Goldspan Dragon—which ensures each Treasure yields two mana instead of one, more than enough to recast the Flameskull and keep the cycle spinning infinitely.