Well, back home, all the other unicorns and I can use our horns to cast magic spells. See? [She points to the horn, and while she's undoubtedly still got it, there's nothing different about it now.]

Here, though, we can't use any sort of magic. Other people have said that special abilities they had at home don't work, or they're not as strong here. I hypothesize that that's one of the ways this place stops us from leaving.