The smallest wing of the Hexagrammaton, the Firewing was dedicated to the bloody subtleties of war.
The hidden blade of the Legion and utilized spies and assassins, formed out of the Host of Fire after the Lion reorganised the older multitude of Hosts into the six wings; It's function went practically unchanged and remained so throughout the Great Crusade.
Within its ranks were a mix of stalker champions and Moritat killers, all bound by their shared expertise in the art of subterfuge. The Firewing sought the destruction of the enemy through the elimination of their command structure and when given free rein upon the field of battle they waged a war of wills, seeking to break their resolve rather than mounting an all-out assault. They considered knowledge amongst the keenest of their weapons, allowing them to strike at the enemy's weak points where their limited numbers could be the most effective. As such, they possessed the most extensive library of any of the other Wings, a vault that contained the accounts of thousands upon thousands of Human and Xenos factions. This vault was in turn guarded by a sub-faction of the Wing dedicated to safeguarding its secrets. During the Second Rangdan Xenocide the Firewing would sustain severe casualties, reducing it to a fraction of its former size.
Of all the Wings, they were the least changed upon the arrival of Lion El'Jonson and many of the eldest marshals of the Firewing were veterans of the Unification Wars and early Great Crusade. The introduction of Caliban influence and recruits did little to change them, and they maintained a policy of recruiting only from Terra and colonies surrounding it. It was also notable for a strong link to the Luna Wolves/Sons of Horus, who recruited from a number of the same worlds. This connection turned to a bitter hatred upon the outbreak of the Horus Heresy.
The role of interrogator-chaplain originated in Host of Fire, and were carried through the Firewing into the Unforgiven chapters of later foundings, even managing to successfully torture information out of a Night Lord Praetor in HH9:Crusade. Though obviously at this point they aren't capturing and torturing confessions out of the Fallen during the Great Crusade.
If the Death Guard are to the Dreadwing as the Iron Warriors and the Iron Hands are to the Ironwing, then the Firewing appears to be the template that the Raven Guard and Alpha Legion appeared to have followed.
The Firewing included unique troops known as the Enigmatus Cabals an odd unit of three jump pack armed Characters each with two wounds who themselves have Preferred Enemy (Characters) as of FAQ, and the Scions of the Firewing rule (Hatred on characters). Clearly intended as an assassin unit, they are armed with needle pistols so they have limited, but reliable shooting against everyone except Death Guard, as well as a special kind of Calibanite blade that can add Rending and Gets Hot if the player chooses, which is probably for the best as most characters will invariably have 2+ saves. They do seem a bit fragile with no room for expansion beyond three, but that's still six wounds, they can do the Deathshroud gimmick of LoS'ing off each other, they have permanent 5+ cover saves and they ignore overwatch if they use their jump packs in assault (where they'll have 5 rending S5 AP3 attacks on the charge). You could also have them be roadblocks who intentionally get charged since they can function like Custodes in that they use their I5 to butcher enemy MEQ's before they get to attack, and their Shroud Bombs ensure they don't take much damage from that charge anyway. A shame they're missing counter-attack.
- Point for point, these guys are straight up better Assault Squads, so long as you don't run into anything that can ID them from range (watch out for Krak Missiles) but they're also not Scoring units, but they're very cheap for what they dish out so if you're going for an assault-heavy list, feel free to load up on them.
- Griffayn ‘The Spear-Cast’ - Voted-Lieutenant of the Firewing, though his rank is held in abeyance. Later pledged allegiance to Luther.
- Vastael - Voted-Lieutenant of the Firewing in the run up to the Siege of Terra. Was so energetic that he was said to be unable to sit still for more than thirty seconds at a time.