User blog comment:PitchBlack696/Alatreon/@comment-207.161.126.113-20110913000607/@comment-3057194-20110916145449

as far as i know you can only get skypiercers by breaking BOTH horns

but if that is too hard: there is an event quest (in MH3) called 'Where gods fear to thread', this quest makes you face an alatreon which is a bit stronger than the normal one, but if you win you will have a high chance of getting skypiercers (and you dont have to break the horns)