Amulet of the Eternal Dragon

The Amulet of the Eternal Dragon is a spitting image of the a severed head of a Dragonborn. It's the remains of a once mighty black Dragonborn. It lets the player extend it's breath weapon attacks both in range, width and damage by the double. If the creature fails its saving throw then roll a d10 twice. The first roll determines extra burn dmg each round. The second roll determines how many rounds. This action makes the player unable to make another breath attack until next long rest and also makes the player exhausted. 

Ex: Cone extends from 15ft - 30ft and hits up to  9 spaces instead of 4.

Line extends from 30ft - 60ft length and 10ft-20ft width hitting up to 12 spaces instead of 3

Notes: Damage: Fire, Exhaustion