This is a retelling of the Unforeseen, but set in the universe from the Season 5 Finale in which Chrysalis has conquered Equestria. You don't really need to have read the original story, but it might help.

Just hatched from his cocoon, a changeling joins the ranks of some of the greatest troops in Chrysalis's army. The Queen has chosen him for a great quest, but an unseen force has other plans. With a voice in his head filling him with ideas contradictory to what Chrysalis wants, the soldier will need to place his trust carefully.