Thunderberd

Electricity magically courses through the weapon along specially channeled grooves in its hollow haft. When you hit with an attack using this halberd, the target takes an extra 1d6 lightning damage. 
This halberd has 10 charges and regains 1d6 + 4 expended charges daily at dawn. While the weapon has at least 1 charge, you can use an action to load a crossbow bolt into its haft toward the bottom of the weapon. Powerful magnetic forces inside the hollow weapon stabilize the bolt and charge it with electricity.
When you take the Attack action while holding this loaded weapon, you can expend 1 or more of its charges to make a special ranged attack with it by leveling and firing the halberd as if it were a crossbow. When you do, you don’t make an attack roll for the attack, and the bolt is magically launched forward from the weapon in a 1-foot-wide line that’s 10 feet long, plus an extra 10 feet for each charge you expend. Each creature in the line must succeed on a DC 15 Dexterity saving throw or take 1d6 piercing damage, plus 1d6 lightning damage for each charge you expend. On a successful save, a creature takes half as much piercing and lightning damage. After the attack, the bolt is destroyed.
If you expend the halberd’s last charge, roll a d20. On a 1, the weapon becomes overcharged and splinters into an explosion of shrapnel, destroying the halberd. Roll a d10. Each creature within 10 feet of the weapon must make a DC 15 Dexterity saving throw. On a failed save, a creature takes 2d6 piercing damage times the number rolled on the d10, or half as much damage on a successful one.

Item type

Weapon, Melee