You sincerely wonder if you're dreaming. It would explain more than a few things. You see a unicorn. Not a horse with a horn glued on its head, this was a unicorn! Its tail was that of a lion, its legs were like a deer's and its cloven hooves, its body gave off a nearly unperceivable ghostly glow. Its coat was a shinning white that gave off a slight mother of pearl gleam. Its mane was like the blue of the sky. Its eyes were sharp and intelligent. And the horn was a long spiral.
Common sense screamed at you to run away. Instead, faced with the impossible, you had to know. Was this a animatronic? A statue? Some poor mutilated animal? Some science experiment? You had to know! It was base human nature!
Moving slowly and more quiet than a mouse, coming from behind as the unicorn is busy grazing.
You reach your hand, and finally, you touch the unicorn's side. Its head snaps back at you, and you feel rooted to the ground in fear, certain you're moments away from being impaled.
The unicorn's spiral horn glows for a moment, it grimaces, then snorts. "Fine. Dammit," it spoke!
Feeling rather startled, and feeling proud for not screaming and running away you say, "Uh, 'fine' what?"
The unicorn sighs. "I'd love to say I'm not to eat you for dinner or some nonsense, but rules are rules. And I considered bad taste to lie to you now. When I say 'fine', I mean, you've caught me. You're sapient, pure-hearted, and a virgin, and you've caught me. That means I'm now bound by stupid unicorn law that says I'm now bonded to you. That means until some time as you cease to be pure-hearted and/or cease to be a virgin, I'm to travel with you and protect until such time as you naturally die of old age. So yeah, sucks to me."