Chainfire

 You can use your action to exhale destructive energy. (15ft cone)

When you use your breath weapon, each creature in the area of the exhalation must make a saving throw, the type of which is determined by your draconic ancestry. The DC for this saving throw equals 8 + your Bramble's Constitution modifier + Bramble's proficiency bonus. 

A creature takes 2d6 fire damage on a failed save, and half as much damage on a successful one. The damage increases by 1d6 every time Chainfire is used. At the end of a round in which no creature has used Chainfire, the damage resets to 2d6.