A fabulous horse is a horse with supernatural powers or a mythical hybrid that is part horse and part some other creature, for example the centaur which has the head and torso of a man and the lower body of a horse.
Legendary horse-like creatures exist in cultures throughout the world. See: a list of mythical horses
They range from the magnificent dolphin tailed hippocampus found carrying sea-gods through warm seas to the sinister each uisge best known for ripping its victims to bloody shreds before consuming them.
See Also: Creatures by Type » Horses