Erin has been plagued with strange, often painful dreams her whole life. She has a strict medication regiment she has to ahere to in order to keep her dreams and the strange other personalty she shares her head with at bay. On her twenty fifth birthday however her life takes an even greater turn for the bizarre when she discovers a cutie mark has appeared on her hips. Princess Celestia's cutie mark. Now she's changing into a pony with no clue as to why, and the only help she can turn to may in fact be her greatest hindrance.
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Set in the TwistedSpectrum's Five Score, Divided by Four setting. If you haven't read it yet I'd recommend giving it a look. Very interesting concept. Though the whole time I was reading it I kept wondering where the Princesses were. He said he didn't plan on using them so I decided I'd have a go at a side-story in his cool universe. XD