User blog comment:Kogath/Monster Hunter Generations Discussion/@comment-8874090-20160811163911/@comment-5569775-20160811195201

It increase Damage dealt to downed large monsters as Narga said, but it also extends the time of your buff type HA's when they are use while a monster is downed. It doesn't work well, or at all(Critical Juncture) for some HA's, but for others can greatly increase the damage, or extend a buff for that extra little bit needed.