Searing Kama

Weapon (sickle), uncommon (requires attunement)
  Inspired by a traditional tanukin kama, this weapon has been obviously modified and upgraded by a talented artificer. It is not unusual for urkin artificers to use traditional weapons as a base for their inventions, combining ancestral wisdom with modern technology.
  Hotting Up. When you deal damage to a creature with this weapon, you gain 1 charge as it begins to gain heat. If you do not deal damage with this weapon for 1 hour, the heat dissipates from the weapon and you lose all charges. You may expend charges to create the following effects:
  Burn! On your turn, you can expend 1 charge (no action required) to deal 1d6 fire damage the next time you hit with this weapon.
  Searing Kusarigama. As a bonus action, you can expend 3 charges to turn the lever on the handle of the karma releasing a whip-like chain in a flurry of sparks. The reach of this weapon increases by 5 feet for the next minute or until retracted (no action required), and your next attack with this weapon has advantage.