Thorned Boar
powerful, intelligent, and incredibly hardy, these unicorns are said to be the ancient steeds of dwarves who would catch them and bend them to their mighty wills so that they could ride them into above ground battle! which has to be a joke, because if you ask any dwarf she'll tell you that no one is stupid enough to try and get one of these things to do ANYTHING it doesn't want to do. sure, they can be easily trained. in theory. but they might not learn what you want them to (or perhaps they'll learn too much) and if they don't like you they'll just leave.
some dwarves keep them, but by "keep" i mean a Sounder of these things decides to peacefully share territory for generations, or specific Thorns bond to specific dwarves for their own reasons and never leave. if you can somehow get that to happen, you're officially a part of their sounder and you have a loyal companion(s) for life. if not?
Stay. The Fuck. Away.