Update 2.4 brought its share of new features to Genshin Impact and in particular the Enkanomiya area . There, many quests are accessible as well as new mechanisms and a new kind of resources to collect called Key Sigils.
Key Sigils are a kind of Electroculus to collect in the new area of Enkanomiya. They will not be used to make offerings to the Statues of the Seven but rather to unlock chests and other puzzles. In Endless Night mode, you will then see symbols on walls (most often) that you can activate by giving the appropriate Sigil-Key.
There are 5 types of symbols and having Sigils of each type will be very useful for you to complete the quest for the Divine Bridle.
Where to find all the Key Sigils of Enkanomiya?
Here is the location of the 54 Key Sigils available in Enkanomiya (the images below are taken from the precious interactive map of Genshin Impact).