All regions in Genshin Impact will have some form of strange item that players will need to collect. In Mondstadt, Liyue, and Inazuma these are Oculi that players can use to unlock new levels of power at the many Statues of the Seven.
The game’s Enkanomiya area is quite different, and instead contains Key Sigils that players can collect. These are broken out into five different types, although all of them look similar and will be marked on your minimap when you are close to them. Enkanomiya is quite a cavernous spot, with lots of caves, tunnels, and jutting rocks, so you may need to change elevation a lot in the search for these.
The Key Sigils are used to open seals that can contain secrets such as items, or even world quests. While they will not grant permanent increases to your character the same way collecting enough Oculi would, they are a great way to gather up resources and items.
If you need help tracking them down, this guide will show you all the Key Sigil locations in the game. You can also use our Seal location guide to find where you need to actually use the Key Sigils to get your rewards.