This is a literal heap of living sand, possessed by the angry spirit of one who became forever lost in the desert. The amount of XP it hands you is not bad at all and the Royal Rings they drop are rather popular among players. To consult their statistics, click the following links:
d) Locate Sand Heaps on the Map
At the time we are speaking, these creatures shuffle around in a realm Kashan which you can access by venturing through the portal at (25,16) in Fenrin Village. This portal also serves as the exit.
This ring is indeed socketed (4 slots) and can be upgraded at your local Blacksmith once you gathered enough xp and money
g) Where do I sell or trade my loot?
Selling Royal Rings should be no problem, if you happen to have more than 8 rings (one for each finger), sell them for 420 coins each at any Jewelry Store
h) A Career
If you like the constant flow of money on your bank account you might want to make a career out of it by becoming a Trader (Class:Trader) which will allow you to sell your items via a Trading Post or even your own shop, see Player Stores.