The pre-equestrian freeze that drove the three tribes on their exodus affected the other races of the north as well. The next hardest hit were the Griffins, one of whom decided that the evil she knew was greater than the evil she had only heard stories about.
When everything you love is gone, and everyone seems to be at fault, sometimes evil turns out to not be evil at all.
Written for the The Equestria Daily Outside Insight Contest.