Neeeeigh!! Neeeigh! How dare they seal me away! I am Equinox! I cannot be stabled! None shall fetter my might!
~ Equinox

Equinox is one of the enigmatic grotto bosses from Dragon Quest IX, and, though it is the least powerful of them all, it is still a formidable foe. Equinox is a death steed of celestial origins, this evil equine seeks to destroy all mortals so that it can once again roam freely in the world.

According to its description, it had a different shape in a certain age (This is a hint to support that Equinox and 9 other grotto bosses are fragments of Zenus).