Thunderhawk

Heavy Crossbow

When you fire and speak its command word, the bolt transforms into a bolt of lightning, forming a line 5 feet wide that extends out from you to a target within 120 feet. Each creature in the line excluding you and the target must make a DC 13 Dexterity saving throw, taking 4d6 lightning damage on a failed save, and half as much damage on a successful one. The lightning bolt turns back into a regular bolt when it reaches the target. Make a ranged weapon attack against the target. On a hit, the target takes damage from the regular bolt plus 4d6 lightning damage.

The crossbow's property can't be used again until the next dawn. In the meantime, the crossbow can still be used as a magic weapon.