In Genshin Impact, after assisting Bona in purifying the Abyssal Corruption from the Chu'ulel Light Core, players must help her find the Primal of Flame. Once located, travelers must offer two Pyrophosphorites (obtained during the Palace of the Vision Serpent Quest) to the Altar of Primal of Flame.
This offering opens a path to Tonatiuh, a floating island above Ochkanatlan’s Cradle of Fleeting Dreams. Reaching Tonatiuh completes the To the Sky-Road Quest and begins The Other Side of the Sky Quest, requiring the collection of four Burning Firestones to acquire the Jade of Return.
Acquiring the Four Burning Firestones:
Burning Firestone #1:
The first Firestone is obtained automatically after the cutscene with Bona concludes. The Little One will collect it; follow it across the bridge (activating the lift mechanism as needed) and interact with the Saurian and Bona. Another cutscene will follow.
Burning Firestone #2:
The second Firestone is on the northeastern island. To reach it: rotate the right and left floating island mechanisms, cross the extended bridge, raise the lift, follow the Little One, collect a Common Chest, activate the mechanism near the Firestone, climb to the upper level, defeat an enemy, collect an Exquisite Chest, open a gate using the mechanism behind the chest, descend to the Saurian, unlock a door, tell the Little One "Let's return to the altar!", and return to the Altar of Primal of Flame.
Burning Firestone #3:
For the third Firestone: rotate the right and northern floating island mechanisms, cross the bridge to the northern island's lower level, follow the Little One, observe the Secret Source Sentinel carrying the Firestone to the southwestern island, proceed to the northwestern edge, become a Qucusaurus, fly to the Pyroculus, activate the tower mechanism, fly to the unlocked door as a Qucusaurus, use the elevator to the upper level, interact with the Saurian, follow it, activate the lift, and return to the Altar of Primal of Flame.
Burning Firestone #4:
The final Firestone is on the northwestern island's upper level. Cross the northwestern bridge (using Bona to adjust it), glide to the northern island's upper level, lower the lift, follow the Little One, tell it "Let's return to the altar!", defeat enemies, return to the Saurian, go back to the Altar, collect a Precious Chest, and finally, return to the Altar of Primal of Flame.
Offering all four Firestones to the Altar completes The Flowing Primal Flame Quest, transforming the Jade of Return into a Golden Entreaty after a cutscene. The Dragon of the City of Flowing Ash then appears, leading to the Nursery of Nightmares island and completion of The Other Side of the Sky Quest, rewarding players with 50 Primogems.