We Didn't Start the Fire

You play a song of in remembrance of trials of old that carries such power it can empower your allies and unleash death on your enemies. When you cast the spell, hostile creaures in a 30 ft. radius of you must make a constitution saving throw. On a failed save, they take 5d8 fire damage and 5d8 thunder damage. On a successful save, they take half as much damage. Furthermore, any allies within this radius gain 1d12 temporary hit points and have advantage on the next attack they make against a creature that took damage from this spell until the end of their next turn. You can use your action to cause the damage, distribute the temporary hit points, and grant advantage as your action on any turn until this spell ends.