Capricorn
Capricorns are a species of aquatic mammals in Eden which were created by the goddess Mira as her answer to her sister’s fearsome fire-breathing dragons. They have the head, torso, and forelimbs of a traditional Earthling goat, but have a fish tail where their hind limbs and rear end should be. They are also far larger than any goat this author has ever seen, rivaling a small horse in size. And it is for that reason that the capricorn is a sought-after mount throughout the waterways of the world.
That, and the fact that their icy breath weapon is one of the only surefire ways to combat the destructive power of dragonfire.
The capricorn’s greatest enemy is not the dragon, however. The sea goat’s greatest enemy is, in fact, dry land. A capricorn which lingers too long on dry land will lose all of its magical abilities and transform into a plain old goat, with no knowledge of its former life—a fate which no amount of re-immersion in water can deny.
Supernatural Abilities
Capricorns are excellent swimmers, but they are also capable of a kind of “flight” during rain storms. They are capable of exhaling an ice-cold breath weapon with a range of 30–60 feet And last but not least, they form telepathic and empathic bonds with any sapient being who mounts them—which sounds great, until you realize that a capricorn will try to drown any rider who brings bad thoughts, nasty feelings, or a disordered mind with them.
The capricorn is a persistent, practical, and incredibly sensitive creature, and it seeks nothing more—or less—than to rid the world of chaos and chaotic thinking.
Super fun. I love the bit where they turn into a normal goat, losing all their specialness, of they're on land too long!
For your consideration, my submissions for the WorldAnvil Worldbuilding Awards 2024. (I've also included some of my favorites other worldbuilders.)
Thanks! That bit was inspired by a bit of mythology I was reading about where that actually happens to the children of a sea goat.