|Universe||Ben 10 Universe|
|Notable Species||Necrofriggians, Psycholeopterrans|
Kylmyys (the Finnish word for coldness) is an ice-cold world and a home planet of the Necrofriggians.
Kylmyys is an icy cold world that was long thought to be uninhabited. It is full of large glaciers and snowstorms much like the Earth's ice ages and it also has many deep caves. Necrofriggians live in the caves on Kylmyys.