Taking the horn from a Unicorn is considered an extremely heinous act. If the unicorn survives, it can no longer use magic, ever. So either way you are taking the pony's life from them.

(Tags used loosely and subject to change)

(Cover Art used from random GISing and belongs to its respective owner(s))

(MLP:FIM and HASBRO are not associated with this story, it is purely for entertainment purposes and not intended for use in any monetary gain)