Eberron: Soaring Skies of Khorvaire
It's a crossbow. That shoots lightning. Enough said, really.
The history of this minor artifact is not particularly well-known and is beyond Mara’s ability to discern beyond the basics of what it does. The X-205 Shootemabob is a masterwork repeating hand crossbow that possesses an enhancement bonus equal to its wielder’s HD/4 (to a maximum of +5 at L20) and automatically reloads itself with a bolt from an integral extradimensional magazine after firing. This produces an effect as if the wielder of the X-205 Shootemabob had the Rapid Reload feat. The integral extradimensional magazine holds up to fifty bolts and reloading it requires a full-round action for every ten bolts being inserted.
Once per day, plus an additional time per five Hit Dice the wielder has, the X-205 Shootemabob can be used to discharge a bolt of lightning. This ability functions identically to the lightning bolt spell, with a Caster Level equal to the Hit Dice. The DC for the effect’s saving throw is 13 plus the mental ability modifier of the wielder’s choice.
Made of some the finest hardwoods you’ve ever seen and embedded with dragonshards, this repeating hand crossbow features a top-fed magazine and bears an extended wrap-around stock embedded with a large Khyber shard that softly crackles with electricity.