Genshin Impact's World Quest Through the Mist is a long one. However, once players complete it, Tsurumi Island will no longer be covered in a layer of fog, and they can freely travel around the island.
In addition, once the Through the Mist quest is done, many side World Quests will be available, hidden or not. One of them is Rero's prank quest, where users fulfill his wish to find a ring and guide him to the afterlife. They will receive a Precious Chest worth 30 Primogems as a reward.
Rero's prank quest complete guide in Genshin Impact
First, you need to complete the whole 'Through the Mist' world quest series in Genshin Impact. It requires a few days to complete as you need to wait for the daily refresh to continue to the next task.
Once all the fog has been cleared, you can find Rero beside a tree northeast of Mt. Kanna. Rero will request you to find his wife's grave to retrieve the ring.
You can teleport to the Chirai Shrine waypoint and head southeast, where the grave is in front of a large tree. There will be a 'Dig' option once you reach the location.
Once you dig the grave, a Thunderhelm Lawachurl will appear behind you. Defeat it to trigger a cutscene and complete Rero's request.
After Rero disappears, a Precious Chest will appear, and you can claim it to obtain 30 Primogems. There are multiple other ghosts whose requests you can fulfill to get a reward, which will be discussed in other guides.