Korok Seed is a material found in Hyrule Warriors: Age of Calamity. It has a standard sell value of X rupees.
In-game description: This small seed was given by a Korok. It has a distinct smell. Gather a bunch of them and surely something will happen...
Obtained by interacting with Korok locations, marked by pinwheels, flowers, leaf-print stumps, small swirls of fairy lights, and other Korok signifiers. Each main story level has some Koroks hidden in it, and so do a few of the challenges. The relevant challenges are listed below.