Where to Get Pristine Cloud Serpent Scale?

This is a rare drop from Rei Lun who appears in the Guo-Lai Halls, Pandaria when the Asssault: The Warring Clans is live. This rare can be killed once per day for a chance at the scale. Reports indicate a 40-minute to 1 hour respawn timer.

How do you get the cloud serpent in Shadowlands?

You must be exalted with the Order of the Cloud Serpent to purchase them. Sage Lotusbloom at the Shrine of Two Moons. You must be exalted with the August Celestials to purchase this item.

Where can I get a Tameable cloud serpent?

Normally these cloud serpents are friendly, but you can make them unfriendly by being in Warmode and using the N'lyeth, Sliver of N'Zoth toy. Then it's just a matter of walking up and taming one of them! You'll find them near the flight master at Mistfall Village.