A souljack is a soul held captive in a suit of armor. Where a common undead is a shadow clamped to the corpse it should have left, a souljack is the inversion of that work on the other side: a soul that should have risen to the Astral, caught instead and knotted into a fabricated shell of white plate and worked bone. The vessel is the body. There is no corpse inside it, only the held strand and the armor it moves. Souljacks make no sound. A soul has no breath to spend on speech, and with the spirit that fled at death gone from it, the thing has no will of its own, so a souljack does only what the working that made it commands.
The making runs against the order of death, which is what makes it hard. At death the soul climbs its astral thread up through the Ethereal Plane toward the Astral, the way a shadow sinks its malstaric thread down toward Malstaris. A necromancer who raises a corpse clamps the malstaric strand through the Nethereal and forbids it the descent. A souljack is the same labor turned on the brighter thread: the binder reaches into the Ethereal, clamps the astral strand, and forbids the soul its rise, fixing it to a vessel built to hold it. The work is Deoric, the titans' command-tongue, and it pays Deoric's two unbending costs. It is paid in titan material, the blood and bone that alone carry a Deoric charge, worked into the runes that hold the clamp. It is paid again in life, the binder's own, spent to speak a command at the soul-binding Azus set over death. None of this is a new magic. It is necromancy worked on the astral thread rather than the malstaric one.
Because there is no corpse to animate, the vessel is fabricated whole. The plate is left white and unblacked, then reinforced with bone taken from the same dead the soul was pulled from. The arms are the tell. They are built long, longer than any living reach, set from leg bones joined end to end and finished with hands, so a souljack stoops and gropes where a living fighter would stand square. Souls come loose easiest where many die together, before the strand has carried them far up the thread, which is why the armorer-binders of Chaal Nazzerox follow armies and work the field while it is still warm. A soul cut from its rise in the first hour comes away clean. One that has climbed too high tears in the taking, and a torn soul holds nothing worth keeping.
An armorer-binder of Chaal Nazzerox, working a field two days after a border skirmish. She moves between the dead with a stylus of titan bone and a shallow dish of dark paste, kneeling at each body only long enough to cut a rune into the breastplate she has dragged off the supply train. Forty suits of white plate stand empty in rows behind her. By the third night the rows have begun to fill, and the ones at the front have started, very slowly, to turn their long arms toward the sound of her voice.
A souljack's strike ignores armor. The long hands close past plate and mail and pull at the spirit-binding of whatever they hold, which is why a souljack deals spirit-damage, the kind no shield turns. The reach is not arbitrary. The thing is itself a creature of bound astral essence, grasping for the same binding in the living. Killing the body it wears accomplishes nothing, since there is no body. To end a souljack you break the vessel that anchors the clamp, and when the armor fails the held soul slips its knot and climbs, late, to the Astral road it was denied. That last fact is a lever a careful party can use. Each souljack is one named death stolen at the threshold of its release, and along the rivers of Chaal Nazzerox the living bury their own fast and burn what they cannot bury, on the chance a binder is working the ground that season.