This story is a sequel to The More Things Change

The five visitors, known as the Crystal Warriors, have found Equestria to be a very nice place to stay. The citizens are kind, the atmosphere is idyllic.

But, now it's time for them to get back to work. Someone from their past has appeared here, and Princess Celestia has tasked them with finding out more about him. Something about him unsettles her, and that can't be good for the rest of Equestria.

Cover art made from Ponylumens
http://ponylumen.net/games/3d-pony-creator/