It's a unicorn

What if it's the dead bones of a unicorn still holding the shape?

"as the last of the unicorns waited for it's soul mate, grass grew on it's hide and it's flesh turned to wood. still the last of the unicorns waits alone for it's soul to be paired"

I just...can't see how that could even be a stump.

What if it's a kelpie?

Could be.....