It’s easy to forget Sigils even exist. They’re a type of regional currency earned from chests or sometimes found while exploring and, if you’re like me, you probably are hoarding them for some inexplicable reason. Stop that. The sigil store (there’s one in Mondstadt and Liyue) offers a finite selection of ascension materials, mora, weapon blueprints, and constellations for the Traveler. Don’t be like me and horde your sigils for no good reason.
Inazuma doesn’t have a sigil store, but it does have the Sacred Sakura. If you offer your sigils there, it will upgrade the level of your electrogranum, allowing you get through higher-level barriers and explore even more of the islands. Like the Frostbearing Tree in Dragonspine, this is also one of the few places you can earn a Crown of Insight—a super rare material that’s required to max out the level of combat talents.