The Apothecary advances on the Savant table as its one Primary — the flesh-smith's mastery of the augmetics that turn a wound into an upgrade. Its Secondary reach opens Ferocity, Leadership, Shooting and the Signature skills, letting the brother who keeps the line on its feet grow a little harder in the fight while his trade stays rebuilding, not killing.
The Captain has the widest Primary reach in the gang, drawing freely from Brawn, Leadership, Savant, Shooting and the Chapter's Signature skills — the strength of the machine, the command of the Iron Council, and the cold gunnery that defines the line. Its Secondary access opens Combat and Ferocity for the officer who must sometimes meet the enemy that closes.
The Centurion advances as the warsuit strongpoint it is. Its Primary draws from Brawn and Shooting — the strength of the machine, and the weight of fire it carries. Secondary opens Combat, Ferocity, Savant and the Signature skills. The sealed warrior rounds out its grind, and never once pretends to speed.
The Chaplain draws Primary from Ferocity and Leadership — the cold resolve of the creed and the will to keep the line advancing. Its Secondary reach opens Brawn, Combat, Shooting and the Signature skills, so the keeper of the creed can harden its own body and gunnery around the exhortation that is its real work.
The Dreadnought advances as the walking heart of the walker line, its Primary access set to Brawn, Combat and Shooting — the raw strength, the melee and the gunnery of the interred hero. Its Secondary reach opens Ferocity alone; the revered dead grind and endure, they do not learn the subtler arts of a living fighter.
Savant is the Librarian's one Primary — the cold intellect that reads the machine cult's logic as readily as it reads the warp. Its Secondary reach runs broad: Cunning, Ferocity, Leadership, Shooting and the Signature skills. The psyker rounds out its discipline as it climbs, though the powers it wields stay its true armament.
The Lieutenant advances as the second officer of the line, its Primary access set to Brawn, Leadership, Shooting and the Signature skills — the same command-and-gunnery spread as the Captain, a step narrower. Its Secondary reach opens Combat, Ferocity and Savant, letting it grow toward melee or toward the machine-craft as the strike force needs.
The Marine is the augmetic backbone of the line, and its skills say so. Primary access runs to Brawn, Shooting and the Chapter's Signature skills — the strength of the machine, steady gunnery, the doctrines that bind the strike force. Secondary opens Combat, Ferocity and Savant. A battle-brother can grow toward melee or machine-craft, and stay the body the whole grind is built from.
The Scout is the one fighter that moves before it grinds. Its Primary access runs to Agility, Cunning and Shooting — the forward, infiltrating edge of the strike force. Secondary opens Savant and the Signature skills. The neophyte starts learning the machine-craft and the Chapter's doctrines, even as his flesh begins its long turn to iron.
The Techmarine is the machine-cult engineer, and its Primary access says as much — Brawn, Savant, Shooting and the Signature skills, the strength of the machine and the mastery of it both. Secondary opens Combat and Leadership. The smith who may one day command the Iron Council can grow toward the fight, or toward the front of it.