Cecilia is an ascension materials in Local specialty in Genshin Impact which is use for ascension two characters.
Description: A beautiful flower with a name that suits it appearance. It only grows where harsh winds blow, and is just as intangible as the true heart of an unbound soul.
What characters use Cecilia?
Beside using it for character you can also use this item to craft Anemoculus Resonance Stone.
Where to find Cecilia?
Cecilia can be found in in Wild area or you can also find this material inside Starsnatch Cliff. Either ways these two locations are the only spots that you can find this item.
The cecilia is a pretty easy item to find in Mondstadt area so try to have it in stacked in your inventory.
In short, If you want to increase Albedo and Venti strength you need make sure that you have a lot of Cecilia in your inventory.