User blog comment:PitchBlack696/Alatreon/@comment-8320770-20130417171312/@comment-8086466-20130427112554

unlike the fight with Mhoran, u already got the ballistic binder with you. It' not shown in your inventory or anywhere, you just can use it. To shoot it, you need to go to the single Ballista on the north (i think it's north).

I was confused too but then figured it out (:

btw it's just real useful if you shoot it while he is flying. Focus on his Head/Wing so he will fall down and be attackable easy on his Horns.