The Heavenly Stone's Debris is the fourth part of The Chasm Delvers World Questline. Part of the quest involves releasing the safety on the cannon's breach, which involves setting three lamp frequencies and operating a giant cannon called the Mountainator.
Make sure that you have read the Safe Blasting Device Signaling Guide, which will tell you that the higher the lamp, the lower the frequency should be. The three lamps are located in the areas marked up in the image below.
How to Set Lamp Post Frequencies
You need to activate the lamps by interacting with them for the first time. After, you can change the frequency of the flicker by interacting with them until you achieve the desired level of frequency.
You can follow the steps below to get the exact frequencies for each lamp, assuming that you haven't touched the puzzle at all. But if you already tampered with them, simply watch the speed of the flicker to gauge the frequency level.
- First lamp (high lamp post): Low-frequency flicker. Interact with it once to activate, and it will automatically set to the correct frequency level.
- Second lamp (middle lamp post): Low-frequency flicker. Interact with it twice to activate and adjust the frequency level.
- Third lamp (low lamp post): High-frequency flicker. Interact with it twice to activate and adjust the frequency level.
How to Operate the Mountaineer
After the lamp posts have been set, follow the quest marker to the Mountaineer. You need to blast off a large boulder by correctly positioning the cannon. To do so, align the cannon until it's facing the direction of the boulder, then make it face down as the cannonball naturally fires higher than the angle of the cannon.
If you haven't touched the cannon at all, move it left once and down twice. Otherwise, you can keep trying until you get it right.
Check out our guide on How to unlock The Lost Valley Domain in The Chasm — Genshin Impact to farm local Artifacts.
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