Captain (Space Marine) - Space Marine Masters: In addition to the command of an entire company, it is common for Space Marine captains to hold a variety of other formal titles and functional duties within the Chapter as what are known as Space Marine masters.It should be noted, however, that some Chapters utilise some of these titles but not others. For example, the Blood Angels have the positions of Master of the Watch, Master of the Marches and Master of the Recruits, but all other company captain titles are unique.Even those who do use these titles do not always follow this exact layout (e.g., the Salamanders' Master of Recruits is the captain of the 7th Company, rather than the 10th, and the Blood Angels' Master of the Marches is the captain of the 7th Company, not the 5th.The following is a list of the most common formal titles held by Space Marine captains in a standard, Codex Astartes-compliant Chapter:Master of Sanctity - The Master of Sanctity, also styled "High Chaplain," is the head of the Chaplaincy in a Space Marine Chapter 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. Immediately beneath him is the Reclusiarch, the head of the Reclusiam. In some Chapters the Master of Sanctity also holds the position of Reclusiarch at the same time, or the two positions are unified into a single role under either title.Master of the Forge - The Master of the Forge is a Chapter's most senior Techmarine, charged with the maintenance of the Chapter's fleet of armoured fighting vehicles, such as Rhinos, Land Raiders and Predators. His knowledge of the arcane sciences has been refined over standard centuries of service, and rivals that of the senior Tech-priests of the Adeptus Mechanicus of Mars. They oversee all of the Chapter's Techmarines and the Chapter Armoury. The Master of the Forge is the chief engineer and weaponsmith of the Chapter.Master of the Apothecarion - The Master of the Apothecarion, also known as the "Chief Apothecary," is the senior Apothecary of the Chapter. As head of the Apothecarion, the Master of the Apothecarion is responsible for assigning Apothecaries to companies, so that they may heal their battle-brothers' wounds or recover the gene-seed of the fallen.Chief Librarian - 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 centuries-long studies and experience, gathered on thousands of battlefields, makes him a crucial advisor to his Chapter and its officers. Chief Librarians often lead forces or assist the Chapter Master in battle while other Librarians aid company captains. The Chief Librarian also holds the overall responsibility for communications as well as scrutinizes battle reports to provide recommendations for honour awards.Master of the Keep - The Master of the Keep is the title of the Space Marine captain who has been designated to serve as the Chapter Master's second-in-command and will serve as the regent of the Chapter homeworld in those cases where the Chapter Master is off-world or has been incapacitated. The title is usually borne by the commander of the elite 1st Company.Master of the Watch - The Master of the Watch is a Space Marine captain who in a Codex Astartes-compliant Chapter serves as the sentinel of the fortress-monastery. He is responsible for the defence of his Chapter's base of operations and homeworld in the absence of the Chapter Master. This title is usually given to the commander of the 2nd Company though the company that is charged with the garrisoning of the fortress-monastery is allotted to a different company on a rotational basis.Master of the Arsenal - The Master of the Arsenal is a Space Marine captain who is charged by his Chapter Master with overseeing his Chapter's arsenal of weapons and munitions. This special duty is traditionally given to those officers who serve as the captains of the Chapter's 3rd Company.Master of the Fleet - The Master of the Fleet is that Space Marine captain who is deemed to have the most experience and greatest skill at planning and executing void-combats. He is given command of the Chapter fleet, and essentially serves as the Chapter's fleet admiral, commanding its flagship and all other space assets when they deploy for major engagements. In rare cases, a Chapter's Master of the Fleet may not be an Astartes officer but a mortal with a long history of space combat and commanding fleet engagements, such as a former or current command officer of the Imperial Navy who has been seconded to the Chapter under ancient inter-service agreements. The title is traditionally given to the captain of the 4th Company.Master of the Marches - As well as leading an entire company of Space Marines in battle, the Master of the Marches has the duty of overseeing the deployment of the Chapter's fighting strength. It is his knowledge of Chapter dispositions the Chapter Master turns to when readying for war. The Master of the Marches is wholly devoted to his duty as he gazes at a massive length of parchment held aloft by a Cyber-cherub, which contains critical data. Upon his backpack are usually integrated twin vox-casters which are utilised to project orders across the noisy battlefield. The Master of the Marches is usually the commander of the 5th Company.Master of the Rites - The Master of the Rites is charged with recording and preserving the martial traditions of the Chapter -- a bombastic, courageous warrior with unswerving loyalty to his battle-brothers. This individual exudes a sense of martial pride and fervour to those around them. A large Servo-skull with an incorporated vox-caster that amplifies his warcries is anchored near his feet by a weighty pair of censers. The Master of the Rites roars inspiring rhetoric during the heat of battle, reminding his battle-brothers to remember their duty and heritage, even as they clash with the foe. The Master of the Rites is traditionally the captain of the 6th Company.Chief Victualler -  The title of Chief Victualler is traditionally held by the captain of the 7th Company. The Chief Victualler is responsible for all of the Chapter's supply needs, particularly those pertaining to food, drink and the other personal requirements of the Chapter's Astartes and Human support personnel.Lord Executioner - The Lord Executioner is the captain who serves as the master of the Chapter's Reserve Close Support Company and is usually the commander of the 8th Company. He is a brutal and direct individual, not so much given to glittering heroics and flamboyant challenges as short, bloody and efficient close combats. Clutching his favoured master-crafted melee weapon in his hands, he strides purposely forward in battle, the expression of a stone cold killer writ on his face as he heads towards his grim duty. His Artificer Armour is often impressively detailed with embossed skulls, scrollwork and multiple Purity Seals. Of all the Space Marine captains within a Chapter, the Lord Executioner is the most menacing.Master of Relics - The Master of Relics is the commander of the Chapter's Reserve Fire Support Company, an unmatched expert in the tactics of long-ranged warfare. He is also the custodian of the Chapter's many technological masterpieces, the most dangerous of which are brought to the battlefield in times of exceptional strife. The Master of Relics is often clad in ancient patterns of power armour, and armed with an impressive array of master-crafted weapons from the Chapter's Armoury. He projects an aura of stoic watchfulness as he directs a withering look upon distant foes. On his backpack is a targeting array which matches the angle of his gaze, gathering telemetry information to be fed to his fire support squads. The Master of Relics is traditionally the commander of the 9th Company.Master of Recruits - The Master of Recruits is the officer who is responsible for training all of the Chapter's neophytes and who usually also serves as the commander of the Chapter's Scout Company, the 10th Company. He will be a skilled Veteran of hundreds of battles and a shrewd judge of character, easily able to determine what will bring out the best in the genetically-altered adolescents who survived their aspirant trials and transform them into true Astartes. As the leader of a Scout Company, the Master of Recruits will be an expert in the irregular forms of combat that define the missions of Space Marine Scouts, including sabotage, infiltration and counterinsurgency.Master of Reconnaissance - The Master of Reconnaissance is the officer who oversees the Vanguard Space Marines of a Chapter, typically from the 10th Scout Company. He is served by two specialist lieutenants with an aptitude for covert operations. The Master of Reconnaissance is often the same captain who serves as the Master of Recruits and the overall commander of the 10th Company.Master of the Signal - A Master of the Signal is an Astartes officer commonly attached to the forward elements of an Adeptus Astartes assault, providing communications support across the wider warzone. He is capable of calling down a pinpoint bombardment from either orbiting fleet assets or static artillery positions nearby, engulfing the foes of Mankind in flaming destruction.Master of the Flag - A Space Marine master title whose function is unknown.