The material below is Open Game Content from a 3PP Source
Horn of the Huntmaster
Aura moderate enchantment; CL 11th
Slot none; Price 5,000 gp; Weight 5 lbs.
This elongated horn curves sharply at the end, almost making it seem more like an enormous pipe than a tool for the hunt. Once each day, a person with the hunter's bond (companions) class feature may blow the horn as a standard action; this grants his full favored enemy bonus (instead of half) against a single target to all allies within 30 feet who can see and hear him. The effect lasts for 1 minute.
Requirements Craft Wondrous Item, greater heroism; Cost 2,500 gp