The Javelin of Lightning was a intricate gold and bronze magical weapon that Vox Machina discovered in the Underdark. It was given to Grog who used it for his rare ranged attacks. The javelin was lost when Grog threw it out of the window of the Cerulean Palace in Ank'Harel and was unable to find it afterward.
When the Javelin of Lightning is thrown and its command word ("Penelope") is spoken, it transforms into a five-foot-wide bolt of lightning that extends in a straight line up to 120 feet. Any creature hit by it must make a DC 17 Dexterity saving throw. On a failed save, they take 4d6 Lightning damage; on a successful save they take half of that damage.