Genshin Impact unlocking the mystery of the stone is part of the mission through the fog and the only way to get the Peculiar Pinion gadget.
After completing the first part of the task, talk to Ruu one day in the real world and you will receive a small gear with some vague instructions on what to do next. Your first task is to find a Seelie.
Genshin Impact solves the mystery of the stone-Electro Seelie location
Go to the mission area, but take care of the Rifthound before doing anything else. They are stubborn and can cause serious harm if ignored. Once they are taken care of, touch Seelie. It’s easy to get lost, but if you do, please walk north along the coastline. You will see it hovering around a group of Samachurls.
Genshin Impact solves the mystery of the stone-activate the stone
Follow it again and it will take you back to the Thunderbird statue. Using the small gear will display a set of symbols on the wall. This is the order in which you should activate the first set of stones, so go to the next quest marker and use the Electro character to activate these stones. Fischl or Sara work best because they can generate electricity without cooling.
The next mission area has its own Thunderbird statue. Use the small gear again and activate the stones from top to bottom in the order it is displayed.
After playing some additional scenes, you need to track some Seelies, but they are easier to find. Talk to Sumida after completing the other requirements to end this mission, and then you will have to wait for another day in the real world to activate the next part of this world mission.
Fortunately, Genshin Impact still has a lot to do. With Peculiar Pinion, you can get some extra treasures by looking for star gems in the area unlocked during A Special Particular Author. If you want to participate in the latest activities, you also need to catch up with the task of the Archon.