Dragon Sensing Longsword

From Princes of the Apocalypse, page 90.

Description
''Weapon (longsword), uncommon. 3 lbs.''

You have a +1 bonus to attack and damage rolls made with this weapon.

This longsword is made of dragon bone and with a dragon-leather grip, and has rubies in its pommel and hilt. The sword grows warm and the rubies glow slightly when the sword is within 120 feet of a dragon.