Putting the pieces together...
The Wyrmhelm: This instrument appears to be fashioned from solid platinum, molded in the shape of a dragon's horn. This lawful good intelligent artifact has Int 19, Wis 10, Cha 19, and Ego x. It functions as both a horn of blasting and a horn of goodness. It never risks exploding when used. The wyrmhelm has 10 ranks in Knowledge (arcana), and can use bless, cure moderate wounds (on wielder), and locate object each 3/day. Created by priests of Bahamut, the Wyrmhelm's special purpose is to destroy the Taumet, and to a lesser extent, any evil dragons that get in its way. Its special purpose dedicated power allows it to unleash a powerful blast in a 60-foot cone once per day. This blast deals 4d10 damage to evil dragons and 2d10 to neutral dragons. Against the Taumet, it deals 8d10 points of damage and forces the Taumet to succeed on a DC X Fortitude(?) save or discorporate into its component relics, killing the host in the process.
The Wyrmhelm has darkvision, blindsense, and hearing to a range of 120 ft.. It can speak Common and communicate telepathically with its wielder, and can read all languages as well as use read magic at will. Caster level 20th.