Imperial Cumulus

An Emperonimbus Cloud is an ancient fossilized cloud which remains in the sky. It was first mentioned in chapter 229. This cloud piles up very high, it does not have atmospheric current, it can never let loose any rain and the sunlight can't penetrate through it. Skypiea is located 10,000 meter above sea level at the top of this cloud. In the Funimation dub, it is called Cumuloregalus.