Heartless Shining Armor: Current Story idea (subject to change)
During the Canterlot wedding, Chrysalis was not revealed and therefor, the two married without a hitch. While Shining was hypnotized, he didn't necessarily need it since he accepted 'Cadence's' change in personalty with very little prompting. He always had some excuse as to why she was acting strange. Stress of being a princess. The demands of the war. Mare problems. No matter how cruel or callous she seemed to be, she would just have to smile that smile he fell in love with and he was putty in her hooves.
They eventually had a child together and for a while, things were good. Said child was smart, strong and pure of heart, just like it's father. But as it grew, Shining noticed that it tended to keep close to its mother more than him. When asked, it just replied that it was going through some things that only it's mother could help with. Tied with this was the sudden flood of reports coming in that something was attacking the inhabitants of the city, leaving its victims listless and dead-eyed. To make matters worse, reports had surfaced that stated that his long thought to be dead sister had been spotted in Canterlot.
Shining was ecstatic, rushing to tell 'Cadence' about it but she seemed to not know who he was talking about. While he hadn't mentioned it for years, he didn't expect his wife to forget such a thing. His suspicions got worse when he noted how the attacks going on were all focused near the castle, as if the monster resided nearby. He then chose to follow his wife one night after she'd assumed he was asleep into the catacombs. All alone, he found Cadence, lying on a bed in chains. He rushed to her side, thinking her to be the mare he married but saw something different.
This Cadence was malnourished, injured and dead. The wounds littering her body were years old and her once vibrant coat was matted with blood, dirt and Celestia knows what else. Holding her in his embrace, Chrysalis arrives, amused by Shining's shock. She explains that she has had the real Cadence locked down here for years, being used as a endless fountain of love for her and her children. That it was only possible because she never stopped believing that he would come for her, would save her. But had finally died a few hours before when she took their child to feed from her. Said child took too much and Cadence's heart stopped from the shock. As the queen gloated, Shining's heart shattered. Not only had he forsaken his beloved Cadence, but he had left her to this hell, believing in his until the very end despite how stupid he'd been. Chrysalis tried to drain Shining of his remaining love, since there was no way for her to hypnotize a pony who knew they were being hypnotized but found his heart empty. There was no longer any love to steal. With a coldness that sent shivers down even her spine, Shining killed Chrysalis just before moving on to hunt down the other changeling's in their mist.
Their child ran away, knowing it's father yearned for its head on a pike. Shining would later return to Celestia's side, swearing his loyalty to her as long as she allowed him to hunt down any changeling as he pleased. He remains a captain in the Equestrian army and fights along side his men.