Scaling weapons, Green Ranger dragon dagger

I'm doing the same weapon but giving it a Destiny twist with the weapon Lord of Wolves. It will deal normal damage but the enemy will roll a constitution save if fail fire damage and disadvantage on rolls because they will hear nothing but loud howls by wolves plus you can play it once a day to summon two flaming wolf companions. For what you're talking about maybe it scales and grows stronger with the more enemies you kill that come from dragon blood or descent. Maybe at one point it can turn into the opposite element of the dragon to do more damage and instead of playing it you breathe in from it and can exhale a breathe attack