Sombra through a miraculous and cruel twist of fate has survived death, leaving the the princess no choice but to imprison him. But, seeing more to Sombra than the anger and hatred that others see in him, Twilight suggests Sombra be reformed. So Luna offers to place him in the care of one of her ponies to help him.
So, Blue Crest, general of the night guard, is given this seemingly impossible mission to reform the former tyrant. But soon, both ponies start to see a different side of Sombra, and both discover that Sombra may be more than they think he is.