Phosphor Weapons (Gee, try and guess what kind of chemical it fires...) are an ancient and very deadly form of unique weapon utilised by the armed forces of the Adeptus Mechanicus. If you haven't guessed by its name, Phosphor Weapons basically fire White Phosphorous in SPESS! though not to be confused with the crawling horror of Phosphex (Radioactive Super-Napalm in Spess) Weapons that are all but forgotten in the Imperium, the blinding white fire of Phosphor weaponry is still utilised by the warriors of the Skitarii Legions to mark out high priority targets amongst battlefield murk.
If those struck by the burning spheres fired by these weapons are not killed by the initial trauma, they are soon felled by the light-guided volley that follows. Phosphor Weapons range from the hand-held Serpenta favoured by many Tech-priests, to the Heavy Phosphor Blaster mounted upon Onager Dunecrawlers. The burning white spheres that shoot out from Phosphor Weapons cling tenaciously to their targets, sizzling wildly as they melt into flesh or burrow through armour and exoskeleton alike. More often than not, it is these luminogenic orbs that deal the death blow. Even if a target proves tough enough to survive the burning pain, the phosphorescent glow these spheres exude can guide an ally's volley to strike the same target.
On the tabletop, generally speaking, Phosphor Weapons have the same strength and AP of a Heavy Bolter, but only single shot. Any wounds or hull points caused on a target will light them up like a christmas tree and reduce their cover save for the rest of the turn. Also makes them easier to charge at by letting you re-roll the charge range. Note: The phosphor pistol and serpenta hit harder and pierce armor better than bolters, in addition to lighting targets up.
So, why did the Imperium drop these? Well, a Tech-Priest by the name of Veriliad destroyed the only STC detailing how to manufacture Phosphex, as he considered the chemical too horrific to use after witnessing its effects first-hand during the ominously-named Cremation of Alcadia Secundus. Naturally, they tied him to a stake and shot him to death with the best Phosphex gun they had, which is now a Relic, the Phosphoenix. This means that the Ad Mech is very reluctant to use their remaining stocks of Phosphex, making the weaker Phosphor weapons the main ones in 40k.
(An argument can be made that the AdMech would have switched to Phosphor anyway simply because Phosphex taints the environment and its self-direction makes it dangerous to friendlies. Phosphor is almost as good, has excellent armor-penetration, aids allies’ co-ordinated attacks, and doesn’t taint stuff or team-kill. And, honestly, Phosphex was probably daemonic or something because damn that shit is nasty and...possibly alive, maybe even a swarm of nanobots.)
There are a few variants of these Phosphor Weapons.
The Phosphor Pistol is the most simple of the Phosphor Weapons, resembling nothing more than a revolver sidearm.
It is one of the primary weapons of the Serberys Sulphurhounds. They are often dual-wielded like an old-western so you can now have your Skitarii to duke it out with the Kelermorph Hybrids. Seriously, GW has been duking out with the revolvers lately, with the AdMech also getting revolver-like weapons from the Galvanic Carbine, the Archeotech Revolver and the larger Phosphor Blast Carbine.
Its ammunition chambers are shorter than the Phosphor Blast Pistol, akin to that of a Phosphor Serpenta, but with a much shorter barrel. This means that the Phosphor Pistol has both have an inferior range than the Serpenta and fires fewer Phosphors per shot than the Blast Pistol. On technical terms, this makes the Phosphor Pistol inferior to its bigger brothers and rightly so.
So why is it still used? Simplicity, maintenance and balance. The Phosphor Pistol is shit easy to repair as the only expensive bits are the ammunition chambers that house the fuel, which also makes it quite lightweight in comparison to its contemporaries. Due to this, the Pistol can go guns akimbo, something neither the Blast Pistol nor the Serpenta could do, doubling its fire rate and damage on an otherwise weak Phosphor weapon.
Phosphor Blast Pistol
A pistol form of Phosphor Weapon that can be used as a sidearm by Skitarii and Serberys Sulphurhound Alphas, the Phosphor Blast Pistol is what you should get when you want to set someone alight but do no want to risk injury on yourself. On the tabletop, these are the Nerf Guns from hell as the pistol format Phosphor Weapon. It is shorter in range than the Serpenta, but you can take it in an infantry squad; no actual blasts, sadly. Design-wise, the Blast Pistol looks like a Pepperbox on hindsight. But upon closer inspection, you can clearly see that what you might have thought were barrels in a pack are actually rather long canisters – in essence, ammunition chambers. So by definition, the "pistol" is actually a very, very big revolver; presumably to be reloaded in a top-break manner, judging by the screw and the little handle attached next to the trigger guard. Of course, this handgun might really be a pistol if you consider that whole pack a one really, really big canister of Phosphex. Or if the canisters rotate at all.
A medium-ranged, pistol-type Phosphor Weapon used by the Sydonian Dragoons particularly to illuminate their would-be targets so that they can easily find and skewer them like shish kebabs, the Phosphor Serpenta is a more fancy looking weapon than the Blast Pistol in both aesthetics and function (And, I dare say... class?). It is so fancy that even a Magos Dominus – a Mechanicus equivalent to a general – can be expected to be holding in one of their many bionic hands. On tabletop, it is 18" Assault 1, essentially your squad's Markerlight when you want to follow up the attack with more shooting and probably a charge as well. Design-wise, in keeping with the steampunk-ish look of the Skitarii forces, it looks more or less like a 19th century revolver had a baby with a flintlock pistol. Considering the ornate theme, the Serpenta likely has a swing-out action which is no different from most of our modern revolvers, if it is a revolver. The center of the cylinder lies more or less at the same level to the barrel, making it more likely to be a single Phosphex canister instead of a conventional revolving cylinder.
Phosphor Blast Carbine
The rifle of the Phosphor family.
The Phosphor Blast Carbine offers longer range and better accuracy than either the Phosphor Pistol or the Phosphor Blast Pistol. It resembles a giant revolver or an elongated Phosphor Blast Pistol (As its name suggests) and is wielded by the Serberys Sulphurhounds.
As the 'middle child' of the Phosphor weapons, the Phosphor Blast Carbine offers both range, firepower and manoeuvrability whilst still leaving the user unencumbered when carrying the weapon. This is important, as the user of the Blast Carbine rides on a giant mechanical fire-breathing dog. As it is basically the big brother of the Blast Pistol, the Blast Carbine use the same canister size as the Blast Pistol.
Essentially, a Phosphor Flamer. The Phosphor Torch is a long Phosphor Weapon that fires a stream of Phosphor at the enemy which completely ignores cover. Wielded primarily by the Pteraxii Sterylizors, these weapons can bathe entire companies in a stream of toxic, pyrotechnic chemicals.
Crunchwise, these Phosphor Torches has a 12″ reach and Assault D6 shots; a pretty nasty Flamer that is S4, AP-1 and deals 1 Damage per shot. Since it autohits and ignores cover and they always come in a flock of five, it is gonna make horde armies squirm with new levels of pain. Plus, the Sterylizors could charge, immediately rolling three attacks at Strength 5 for the weapon. Horde army melter indeed.
A rapid firing Phosphor Weapon that is used as a secondary weapon by Kataphron Destroyers. Much larger than the Phosphor Blast Carbine and with a longer range, albeit far more cumbersome and heavier.
The weapon is equipped with a box-magazine filled with Phosphor canister-belts. Unlike the smaller Phosphor weapons, which most likely fires the Phosphor itself as a projectile, the presence of an ammo belt suggest that the Blaster fires the entire canister like a grenade launcher, or in this case, an exploding Willy Pete round for real-world comparisons.
On the tabletop, it is overall similar to that of the Phosphor Serpenta but it is now 24" and Rapid Fire. You know, just so you want to punish whoever is unfortunate enough to face it. Because the Serpenta version isn't already powerful enough and you just want to be sure that target is dead.
Heavy Phosphor Blaster
A large type of Phosphor Weapon that is deployed on Kastelan robots and in a twin mount on Onager Dunecrawlers. The Heavy Phosphor Blaster is also found twin-linked and as one of the primary weapons of the Archaeopter Stratoraptor.
Like the smaller Phosphor Blaster, the Heavy Blaster is fed through a ammo-belt system. However, it can either be housed in a box-magazine, a sickle-magazine or, if it is large enough, an internal magazine.
Crunchwise, if you thought the regular Phosphor Blaster was bad, this thing not only takes the cake, it fucks the baker's newlywed spouse as well. On the tabletop it is a decend all rounder, 36" Heavy 3 S6 AP2 for fucking Guard over (wounding on 2s and ignoring saves completely), and it ignores cover. Probably the best Luminagen gun. It can be argued to be overcosted however, being still only D1.