When Luna became Nightmare Moon, it was not of her own volition. She was sick. She was angry and scared, but mostly, she was sick. And when she needed help the most, she was abandoned by the only pony who could understand her fully. Now that she's back in Equestria, she doesn't feel she can trust her own sister. And if the magnanimous Princess Celestia can't be trusted, who can be?
Trigger Warnings: Depression and self-harm.