#techmarines

Firstly, the ranks of Librarians (as defined by 40K itself).

Librarius

A Librarium, or Librarius is the command and communications center of a Space Marine Chapter's fortress-monastery, and the repository for centuries of wisdom and history, culled from the reports, treatises and memoirs of the chapter's greatest warriors and finest minds.  Most of the servants who work in the Librarium are psykers - those who are full battle-brothers of the chapter are known as Librarians.

Lexicanium is the lowest rank of Space Marine Librarian. This rank is given to those who have recently joined the Librarius and are given duties related to the creation of battle reports to submit to the Chapter's records. These summary accounts chronicle the history of a Chapter and can vary in nature, depending on the Lexicanium's beliefs and philosophy or the campaign.  Lexicaniums are often distinguished by their lack of a psychic hood or even helmet, appearing very similar to their brother-marines except for the blue Power Armour that Librarians wear. A typical chapter should maintain approximately 5 members of the Lexicanium rank.  They serve with reserve companies and amongst the chapter's holdings, both relatively 'soft' positions that allow them to focus and expand their psychic potential.

Codiciers are the second rank of Space Marine Librarians.  Their tasks include evaluating the reports written by the Lexicanium and finalizing them for inclusion to the Librarius, as well as providing strategic overviews of campaigns. A typical chapter should maintain approximately 5-6 Codiciers at any given time.  They serve on the front lines with the battle companies and advise their captains directly.  

Epistolary is the third rank of Space Marine Librarians. Their primary role is chief communications officer, both on the battlefield and beyond. They are able to use their powers to project their mind through the warp, similar to the Astropaths of the Adeptus Astra Telepathica, but without the need to endure the torturous ritual of soul binding that is otherwise required. More commonly, their abilities are used over shorter distances, coordinating attacks and battle orders. A Codex chapter should seek to retain approximately 5 men of Epistolary rank.  These are veteran marines of crucial importance to the chapter, and are often granted the use of terminator armor which underscores their weight of rank.

The Chief Librarian is the strongest and most psychically attuned Librarian of a Space Marine Chapter.  He is master of the Librarium and has full access to otherwise restricted parts of it that house the Chapter's most powerful and dangerous relics. His century-long studies and experience, gathered on thousands of battlefields, makes him a crucial advisor to his Chapter and its commanders.  Chief Librarians often lead forces or assist the Chapter Master in battle while other Librarians aid company Captains. He also holds the overall responsibility for communications as well as scrutinizes battle reports to provide recommendations for honour awards. Different chapters use different means of choosing a Chief Librarian.  Typically, an auto-seance followed by a reading of the tarot is conducted to determine which of the chapter's Epistolaries will ascend to fill the position.  On rare occasions, an individual librarian will demonstrate such cunning or strength of mind that they ascend by fiat, with the librarius unanimously agreeing on the Emperor's chosen candidate.

Approximate recommended number of librarians per chapter of 1000 marines: 15-20

Apothecarion

The Apothecarion is a Space Marine Chapter's medical and bio-engineering department. Their most important duty is the preservation of the Chapter's gene-seed, the only means by which new Space Marines may be created. The life or death of a Chapter is therefore dependent upon their Apothecarion.

Apothecary Medics are battle brothers who have shown the proper inclination towards the preservation and care of the lives of their brethren that they have been inducted into the ranks of the chapter apothecarion.  They are trained to stabilize and heal grievous battlefield injuries, pulling their squad mates back from the brink of death.  A major undertaking by the chapter (anything consisting of at least three squads to a full company) will never set off without an apothecary medic amongst their number, barring the most extreme circumstances or dire emergency. A chapter typically maintains a bare minimum of 10 Apothecary Medics. An Apothecary Chirurgeon is a fully-qualified member of the apothecarion.  They are fully trained in the methods of overseeing new inductees to the chapter, skilled at delicate procedures such as limb reattachment and regrowth, and are trusted by their chapter brethren to maintain the health and welfare of the chapter. A typical chapter maintains no fewer than 10 apothecaries.

An Apothecary Chymist is the most revered amongst their brethren, as their title reflects the trust their chapter has placed in them by granting unto them the wisdom necessary to maintain the great vaults in which the chapter's gene-seed is stored, maintained, and studied.  If their lower-ranking brethren can be said to maintain the current health of the chapter, Chymists maintain the chapter's future. A typical chapter maintains approximately 5 Apothecary Chymists. The Chief Apothecary (sometimes called Master of the Apothecarion or Apothecary General) is the head of the apothecarion.  He is chosen by seniority, having garnered decades upon decades of experience both on the battlefield and in the inner workings of the chapter's banks of gene-seed and records. Approximate recommended number of apothecaries per chapter of 1000 marines: 20-25

Techmarines

In addition to being battle-brothers to their fellow Space Marines, Techmarines (Frater Astrotechnicus) also serve as mechanics and technicians to their respective Chapters, similar to the Enginseers who serve in the Imperial Guard.

The Techwright is a space marine that has shown some talent for the workings of machinery and the mysteries of technology.  At their induction to the fratery of the chapter's techmarines, they are permitted to aid in the maintenance and repair of wargear such as bolters and power armor.  Despite this honor, however, a Techwright is not permitted to rise any higher in the heirarchy of the Cult of the Machine until they have undertaken the ritual pilgrimage to Mars to be initiated by the Adeptus Mechanicus themselves. A typical chapter maintains 5-10 Techwrights.

Technologists are those marines that have both made the hallowed journey to Mars and received the approval of their superiors to continue along their chosen path.  They are now fitted for a servo-harness and permitted to work on the chapter's hallowed fighting vehicles, such as, bikes, transports and aircraft. A typical chapter maintains a corps of approximately 10 Technologists.

Technomancers are the most hallowed of techmarines, inducted into all but the most closely-guarded secrets of the machine.  They are permitted to command retinues of battlefield servitors, and granted leave to see to the well-being of the chapter's fleet and fortress defenses, as well as the care, wakening and sedation of the revered dreadnoughts. A typical chapter maintains approximately 10 Technomancers.

The Master of the Forge (sometimes shortened to Forgemaster) is the overseer of all a chapter's wargear, a weaponsmith beyond compare.  He is elected from amongst the Technomancers, typically chosen by virtue of his exemplary record or superior intellectual capacty.  Virtually no secret of technology remains unknown to him, however oftentimes he is so far advanced along the path of the machine that his eccentricities and inhuman nature make him an outcast presence at the chapter council.  Despite that, his expertise and vast experience give his voice much weight in the ears of a wise Chapter Master.

Approximate recommended number of techmarines per chapter of 1000 marines: 30

Chaplaincy

Space Marine Chaplains are the spiritual leaders of Space Marine Chapters. Warrior-priests, they fight alongside their battle-brothers, chanting the Chapter's sacred battle creeds, and inspiring their brethren to greater feats of bravery. To enemies they appear as terrifying and sinister figures in black power armour and skull-visaged helmets.

Vicars are the youngest to hold office in the chaplaincy.  Often firebrands, their ferocity is typically fueled by the implantation process which leaves newly-made marines bursting with aggression.  As such, Vicars often make use of jumpacks, serving with assault squads in the reserve companies.  Their strident calls for the destruction of the foe encourage their fellows to greater acts of courage and heroism that will see them advance into the chapter's fighting companies. A typical chapter maintains between 5 and 10 Vicars, depending on recent casualties. Canonists constitute the bulk of a chapter's chaplaincy, so named because it is their rhetoric that informs the tone of the chapter's religious beliefs.  Solid and dependable men, Canonists chiefly concern themselves with the spiritual health of their company brethren, seeing to them when their faith falters or false witness leads them awry. A typical chapter maintains no fewer than 10 Canonists, ensuring that a minimum of one can attend each company in dire circumstance. Precentors are the highest-ranked chaplains.  To them falls the duty of selecting new inductees and ministering to the chapter as a whole, space marines and chapter serfs alike.  Precentors of more religious chapters maintain the written testaments by which the faith and morality of their brethren is shaped.  Precentors loom large over their flock, not least because they are often entrusted with their chapter's hallowed suits of chaplain terminator armor. A typical chapter maintains 3-5 Precentors. A Reclusiarch is one of the senior members of the Chaplaincy in a space marine chapter. The immediate subordinate of the Master of Sanctity, the Reclusiarch is charged with overseeing the Reclusiam, the holiest place in the fortress-monastery which houses the chapter's holiest relics. The Reclusiarch also oversees the rituals pertaining to the relics.

The Master of Sanctity (also known as High Chaplain) is the head of the Chaplaincy in a Chapter of the Adeptus Astartes and head of the chapter cult. One of the masters of the chapter, the Master of Sanctity oversees the spiritual health of the chapter by assigning Chaplains to the companies.

Approximate recommended number of chaplains per chapter of 1000 marines: 20-25 Non-codex or codex-divergent chapters occasionally alter or combine the roles of various specialist roles.  Wolf Priests of the Space Wolf chapter combine the roles of apothecary and chaplain, while Iron Fathers of the Iron Hands combine the roles of chaplain and techmarine.

Other chapters maintain a specialist apparatus of unusual size or reverence.  The Blood Ravens have a great many librarians and sometimes permit them to hold command roles, even ruling over the entire chapter.  The apothecarion of the Red Scorpions is held in great regard, with individual apothecaries assigned almost to the squad level.  The Storm Wardens keep an unusually high number of techmarines amongst their ranks due to the chapter's many fighting vehicles.  The Dark Angels and Blood Angels chapters assign particular value to their chaplains and apothecaries, respectively terming them Interrogator-Chaplains and Sanguinary Priests.