In the human lands, some humans believe in the devil (he's like a really bad spirit) and that he has horns, much like elves. It makes you think sometimes. It's kind of sad.
Which part is sad, love? That people believe in this bad spirit, or that he has elf horns?
Xadians believe in various dark and powerful beings, and plenty of them are horned like we are. People--elves and humans alike--tend to describe the things that threaten their daily lives by assigning them traits they consider bad, so they can train themselves to guard against them. But they also assign them familiar traits, even if they don't mean to. The trick is figuring out which is which!
Are the horns what make this devil bad? Are your sheep evil, or your lizards? Surely not. Horns are just horns, and many creatures have them. What makes something evil is what lies in its heart, not in its form.
If your belief a mythic creature's existence teaches you to distinguish between what is good and helpful and what can hurt those you love, does it truly matter if the creature is real?
Choose your mythic creatures wisely, though, with an eye to the people you'll be sharing your belief with. It doesn't matter who you believe in. What matters is what you do as a result of that belief.