Twilight's Futa Spell

After a bit of research, Twilight learns of a new spell in the Canterlot Archives. With no other pony around to test it, why not see what happens right then?

When Twilight learns of a new spell that was hidden by Starswirl the Bearded, she decided that the only way to find out what it does is to test it out. Being alone and surrounded by such knowledge might be the best environment to do such. Of course, it could have some side-effects.

Contains: Futa