This is a rather unexpected cover done for The Three Sisters: Extended Family
by Wanderer D
. This was originally meant to be a small sketch of Pupa/Rarity/Purity inspired from the series, but imagine my ecstatic surprise to find out that he used it for the next story in the series! I was about to die from happiness at that point.
Fan gushing aside, I suggest you give the series a reading. It's a very sweet story throughout. "Choosing whether or not to visit Chrysalis has been bugging Rarity for a week since receiving an invitation to do so. But there seems to be trouble brewing in the Hive and Rarity now has little time to act. Either way, her family's future rests in her hooves."
Also, some bonus content for anyone that wants to see the rest of the sketches. Some possible spoilers, please view with discretion! [link]