Black packs are pincer-like in shape, and may be closed when not in use or opened ready to fire. The weapon fires a sheet of web-like energy which instantly vaporises a target on contact, unless it has been de-carbonised such as is the case for Divine Assassins.
At least some black packs, such as those carried by the security drones, are able to fire non-lethal discharges to stun their target.
Energy discharges from black-packs can be fired on a much larger scale in ship-mounted weapons as seen on the Foreshadow and Megashadow, both of which have far larger versions of the weapon capable of destroying most ships instantly, or entire planets after successive bombardment. The technology appears to originate from the Insect Civilisation, as His Divine Shadow demonstrates an innate ability to fire a similar energy discharge.
The black pack first appears in Lexx 1.1 "I Worship His Shadow" when the Foreshadow uses its ship scale black pack weapon to destroy Brunnis-2. Later in the same episode, ordinary black-packs are shown wielded by the security drones on the Cluster, and stolen by Thodin and his rebels, though they ultimately have no effect on Kai when he confronts them. Another ship scale weapon is shown when the Megashadow pursues the Lexx at the end of the episode.
Another display is seen in Lexx 1.4 "Gigashadow" during a flashback to the destruction of an Ostral-B outpost. Stanley Tweedle was on route to the outpost when the Megashadow arrived, destroying the outpost with a ship-scale weapon similar to the Foreshadow's, leaving Stan stranded in space.
Black packs later appear in Lexx 2.4 "Luvliner" when a bounty hunter arrives to try and steal the Lexx, using it to blast into rooms of the Luvliner and kill several innocents, and in Episode 2-15 Woz. where they are used by both the forces of the Wozzard and the forces of the Dark Lady.
In Lexx 4.19 "Haley's Comet", 790 reveals the location of an abandoned black pack on the Lexx to a disgruntled Haley who then proceeds to use the weapon to kill several of the "friends" who had betrayed and used her. Presumably this is the same black pack left by the mercenary from Episode 2-4 Luvliner.