In Genshin Impact, after assisting Bona in purifying the Abyssal Corruption from the Chu'ulel Light Core, players must help her locate the Primal of Flame. Once found, 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.
Obtaining the Four Burning Firestones:
Burning Firestone #1
The first Burning Firestone is obtained after a cutscene with Bona on Tonatiuh. The Little One will retrieve it; follow it across a bridge (using a lift mechanism) and interact with the small Saurian before speaking to Bona.
Burning Firestone #2
The second Firestone is on the northeastern isle. Activate the floating isle mechanisms to extend the bridge, raise the lift, and follow the Little One. Along the way, collect a Common chest. Activate a mechanism near the Firestone, climb to the top of the tower (defeating an enemy), collect an Exquisite chest, and open a gate using another mechanism. Interact with the Saurian, unlock a door, and return to the Altar.
Burning Firestone #3
To obtain the third Burning Stone, manipulate the floating isle mechanisms to reach the northern isle's lower level. Follow the Little One, observing a Secret Source Sentinel carry the stone to the southwestern isle. Ride a Qucusaurus to reach the Pyroculus, activate a tower mechanism, and use the Qucusaurus to reach an unlocked door. Activate the elevator, interact with the Saurian, activate the lift, and return to the Altar.
Burning Firestone #4
The final Firestone is on the northwestern isle's upper level. Cross the bridge (using Bona to adjust it), glide to the northern isle's upper level, lower the lift, and follow the Little One. Defeat enemies, return to the Saurian, collect a Precious chest, and finally, return to the Altar.
Offering all four Firestones to the Altar completes The Flowing Primal Flame Quest, transforming the Jade of Return into a Golden Entreaty. A cutscene introduces the Dragon of the City of Flowing Ash, leading players to the Nursery of Nightmares to finish The Other Side of the Sky Quest and receive 50 Primogems.
