To my most faithful student, Twilight Sparkle,
Twilight, I will choose to believe that neither you nor your actions have caused the spacial rift, nor the eventuality of you falling into one. I will also choose to believe that all of recorded Equestrian history is lucky enough to have never encountered a similar circumstance, or at least never quite managed the portion of reattaching the soul to a cadaver apparently without access to magic.
I choose to believe these things because Discord disavows all involvement.
So. Luna is on a 'business trip' at the moment, so do try to avoid causing another zombie panic, and I'm afraid my skill in necromancy extends to identifying it, and eradicating it with extreme prejudice.
Please bear in mind you are currently classified as 'undead' so do avoid the usual countermeasures until Luna can sort this out.
Your loving mentor,
Princess CelestiaPS. Twilight I love you, but you're why I cannot take a vacation.