The Inazuma region is filled with all kinds of secrets and one you might stumble across is the Stone Lanterns and the Genshin Impact Orobashi's Legacy questline. You'll only be able to access this questline by getting to the most southeast Yashiori Island. This quest will help you stop the ever-present storms on the island, as well as net you some pretty great loot. The questline is told across five different parts, all of which are listed below.
Genshin Impact Orobashi's Legacy - Prologue
Here's the easiest portion of the quest. For the prologue, you'll simply be starting the quest by talking to Kaji. On Yashiori Island zoom into the map and find where it says "Fort Fujitou", if you head directly right from those words you'll run into Kaji who has a blue exclamation point. He'll explain that the Stone Lantern Wards need to be repaired around the island and that you should start with the one directly to his right.
If you happen to inspect the Stone Lantern before speaking with Kaji you'll get the following message:
Travelers passing through: if you have any questions about this ward, please go to the Musojin Gorge and talk to Mr. Kaji about it.
Each portion of the quest going forward will have you completing a number of tasks normally consisting of defeating some enemies, and completing puzzles by directing Electro energy through the Stone Mound and Thunderbearer Mirror (which I will simply be calling pylons going forward.) Doing this will help you recover the Rock Pillar Warding Stone and Rock Pillar Pearl which will fix the Stone Lantern.
Genshin Impact Orobashi's Legacy Part 1 - Fort Fujitou
The first of the Pylon puzzles begins directly to your left after communicating with the Stone Lantern. You'll need to approach each pylon to change its orientation or angle of fire. The aim here is to create a daisy chain where the electro ball can go down the chain and end up hitting the large spherical water barrier further down the slope. The path you need to set the electro ball to take is as follows.
After you've destroyed the water barrier you can obtain the Pearl where it's floating in the middle of the newly created opening, and you can drop down into the pit to fight off an enemy and claim the Warding Stone. After obtaining both of these items return to the Stone Lantern and repair it, talking to Kaji will then give you Part 2 and Part 3 of the questline.
Genshin Impact Orobashi's Legacy Part 2 - Serpent's Head
Head to the marked location to find the Stone Lantern and Paimon will recommend you use elemental sight to find the missing pieces
Rock Pillar Warding Stone
To the left of the Stone Lantern, there will be a hole you can drop into, before you hop in grab an Electrogranum to pass through the Thunder Barrier and lower the water level below.
Watch out for this electrified water, it will kill you SO quickly
Once the water level has dropped defeat the three enemies and solve the trigger puzzle. This will not only spawn a chest but also open a grate allowing you to descent even further into this ruin. where you can get the Rock Pillar Warding Stone.
Rock Pillar Pearl
To the right of the Stone Lantern follow the elemental trail to find another sequence of pylons that you're able to adjust to complete a path and unlock the Rock Pillar Pearl. The solution for the pattern of Pylons is shown below.
Now that you have the Warding Stone and Pearl you can go ahead and fix the Stone Lantern. After fixing the Stone Lantern once again the skies will clear and you won't need to worry about dodging lightning.
Genshin Impact Orobashi's Legacy Part 3 - Jakotsu Mine
Track this quest and head towards the marker to find that the last of the Stone Lanterns is inside one of the water spheres. As you floated down to the bottom of the mine you will have seen another puzzle involving the electro pylons. Direct the pylons towards each other as shown below.
Once you've got access to the Stone Lantern interact with it and then use your Elemental Sight to find the pieces to repair it.
Rock Pillar Warding Stone
To the left of the Stone Lantern, follow the path up the hill a bit. You'll end up in a room with a Luxury Chest in the middle and a lot of Electro Sigils around (some are fake but this is a really easy Luxury chest to obtain.) Climb to the top left ledge in this area and you'll find the Warding Stone.
Rock Pillar Pearl
To the right of the Stone Lantern, follow the path and you'll come to a cave with a few enemies and the Pearl floating in the center of a thunder shield. Defeat the enemies to activate the Electrogranum tree giving you access to the Pearl. Once you've deactivated the thunder shield three more enemies will spawn, take them out too. Climb up a nearby wall and drop down to pick up the Pearl.
With both items, you can return and fix the final Stone Lantern. Now it's time to meet up with Kaji at the westernmost point of the island as previously promised.
Genshin Impact Orobashi's Legacy Part 4 - Fort Mumei
Head to the waypoint marker and Kaji will tell you that the ruins of Fort Mumei are now rising our of the water. There's one more pilon puzzle here for you to solve. Each of these Pylons is in the water so summon the waverider. Being on the water it does seem like this is going to be a harder puzzle, but you really just need to link them all up in a counterclockwise symbol around the newly raised central platform.
Clear the sphere from the center of the area and you'll need to fight Maguu Kenki waiting for you in the center. The fight is completely done in ankle-deep water so plan for a lot of water elemental combos. He will use his sword to attack you as well as the rotating masks. He'll routinely use ice-based attacks too, these will freeze you if they connect.
Once you get Maguu Kenki past 2/3 of his health he'll start creating clones of himself and attacking twice as much. Make sure to use your stamina sparingly so that you can dash away as these attacks will cover a lot of the arena.
Once Maguu Kenki has been defeated the two items to repair the Stone Lantern will be in the arena. The Pearl will be floating above it, and the Warding Stone will be in the ground near the back of the arena. With those two items placed in the final Stone Lantern the skies over the island return to normal.
Speak to Kaji once more and he'll give you a reward for completing the quest. For your troubles you'll receive 50x Primogems, 6x Hero's Wit, Diagram: Kitain Cross Spear, and 60,000x Mora. The Kitain Cross Spear diagram can be read to allow you to forge the Kitain Cross Spear at a blacksmith.
The Kitain Cross Spear is a 4-Star Polearm weapon that has a base attack of 44. It has an effect called Samurai Conduct that will increase Elemental Skill DMG. When your elemental skill hits an opponent the character will lose 3 energy but regenerate 3 energy every 2 seconds for the next six seconds. You can use this effect every 10 seconds.
Congratulations on completing the Genshin Impact Orobashi's Legacy questline!