Javelin of Lightning
Amber found on a stormy day at the beach
Once per dawn, when you throw this magic weapon and speak its command word it transforms into a 5-foot wide line of electricity that is 120 feet long. Each creature in the area (excluding you) makes a DC 13 Dexterity, taking 4d6 lightning damage on a failed save, or half damage on a success. The target of your attack takes the javelin’s normal damage plus 4d6 lightning damage.