Merir Astelan - Luther the "Arch-Heretic": Chapter Master Astelan was an able commander and a veteran and experienced Astartes. He had been present when Sar Luther, the Lion's adoptive father and chief lieutenant, was made the Guardian of Caliban. Luther had supposedly been honoured by the Primarch for showing him such faith and trust as to leave him as the protector of the Legion's homeworld. But the aggrieved Luther had grown bitter by what he viewed as his sidelining from the glory of the Great Crusade, for a seed of jealousy and envy had been planted within him ever since the Emperor had first arrived upon Caliban and everything had changed forever for the knights of The Order.When the Emperor had first arrived, and the Dark Angels were given to El'Jonson to lead, Luther had wept that he was too old to become a Space Marine. The Emperor sent his best chirurgeons and apothetechs, so that those members of The Order who were too old to be implanted with the Primarch's gene-seed might still be given many of the benefits of the Astartes' gene-altered bodies, living long past their natural deaths and capable of great feats of arms.But Luther was never and could never be a true Space Marine. There were few who listened to him, most of them of the new Legion. Astelan and the Space Marines of the Old Legion, while having the deepest respect for Luther and his great achievements, had served under the Emperor Himself and owed their loyalty to Him and Him alone. Yet, when they were left behind on Caliban, Astelan and the other Terran-born Dark Angels stood beside Luther and offered him their full support.Nearly fifty Terran years later, bear the 200th year of the Great Crusade, a rebellion broke out on Caliban, with certain sections of the indigenous population rising up against Imperial rule. While Luther was initially unwilling to commit his Legion garrison forces to combat his own people, he was eventually forced to use Astartes troops to investigate serious matters, such as the disappearance of the entire workforce and Imperial Army protection detail of a petrochemical plant.Luther's lieutenant, the Librarian Zahariel El'Zurias, was tasked with this undertaking and called for volunteers. Merir Astelan was one of the first to step forward, and Zahariel was glad to have the veteran along on the mission, though he was a little curious as to Astelan's chosen battle-cry -- "For Luther!" Zahariel and Astelan's force ultimately confronted and destroyed a local group who had been tainted by Chaos, and both agreed to raze the entire site in the aftermath of the incident in order to keep what they had discovered from wider Imperial authorities other than Luther and the Dark Angels' Caliban command.In the aftermath of this discovery, tempers grew frayed amongst the Calibanite Legion command staff, principally between the Terran Librarian Israfael and Luther himself. These tensions became clear as the staff deliberated on what course of action to take in the wake of the Chaos taint and where potential blame for the incident lay. When Israfael became particularly strident in his disagreements, Astelan was observed by Zahariel as reaching for his weapons, prompting the shocked, younger Librarian to intervene to keep the peace between his brothers. Immediately afterwards, Luther placed Astelan in personal command of Caliban's Planetary Defence Forces and ordered him to place the garrison on a war footing.Not long afterwards, the political situation on Caliban deteriorated further when the Northwilds Arcology came under assault by a force of apparent zombies from the depths of the planet. Rioting broke out as native Calibanite Astartes and the Terrans sought to lay blame or suspicion for the unfolding events on each other, and the local defence forces and rebel soldiery became involved, with battle lines and relative loyalties sorely tested.Astelan was present at another meeting of the Caliban commanders called as a result of the rising tensions, and was therefore witness -- along with Zahariel, Israfael and the Lord Cypher -- when Luther revealed that he had lost faith in Lion El'Jonson. When Israfael broke ranks and moved to attack Luther, Astelan attempted to subdue the Librarian with the butt of his pistol, but was telekinetically flung across the room for his trouble. Surviving the melee that saw Israfael defeated and critically wounded with no further harm, Astelan was then tasked by Luther with arresting all the senior Imperial authorities on the planet, including the commanders of the Imperial Army and Mechanicum forces stationed there. Astelan hesitated for a long moment at obeying such an openly treacherous order, but eventually agreed to carry it out.After Luther had completed his subsequent effective complete takeover of Caliban, Astelan was contacted by one of his company commanders, Captain Melian, with concerns about the direction events were taking on the planet, particularly that new Legionaries were being sworn to defend Caliban instead of swearing allegiance to the Emperor of Mankind.Astelan expressed ambivalence about Luther's changes, pointing out that as a force ordered to remain as a garrison on one world without naval elements and apparently forgotten by the rest of the I Legion, the Calibanite Dark Angels were effectively irrelevant to the progress of the Great Crusade and so might as well take as much pride as possible in being the core of Caliban's Planetary Defence Force.However, on learning that Captain Melian spoke for a group of officers and Veterans in his command who were preparing to take militant action against Luther in order for their concerns about his possible treachery to be recognised, Astelan agreed to aid them in planning a more legal and bloodless move against the planetary commander. He suggested commandeering a secondary communications spire and sending messages to Terra and the Lion requesting restoration of the original Legion protocols and command structure until the Lion could assay the situation personally, while simply detaining Luther under close arrest.His plan was agreed upon by the conspirators, though not without them warily noting that, under old Legion protocols, Astelan would become the force commander. Regardless, the plan was carried out; the bulk of the conspirators would head to the spire as part of a "live ammunition training exercise," while most of the ringleaders, including Astelan, would confront and arrest Luther. Luther was surprised by Astelan's presence in the delegation that came to seize him, and also by what happened next.Astelan contacted the commander of the Imperial Army forces garrisoning the tower -- Marquesa-Colonel Tylaine -- and ordered her to proceed with their previously agreed-upon plan. The Imperial Army forces and a company of Dark Angels under the command of Astelan's subordinate, Captain Galedan, suddenly attacked the conspirator's column. As the realisation dawned that Astelan had only joined the conspirators so he could defeat their plans from within, Luther joined Astelan in turning upon the ringleaders, and with him, slew them all. Most of the conspirators surrendered rather than fight other Space Marines, and the little rebellion was over before it could truly begin.There were so many prisoners of the rebellion that there wasn't enough space for them all in the dungeons of Aldurukh. Astelan counselled that Luther simply carve out new ones within the fortress-monastery's rock. Luther also questioned why Astelan had allowed the conspiracy to get so far along, rather than just reveal it to him immediately, suspecting that Astelan might truly have wished to overthrow his authority and only switched sides to curry favour with him. After all, according to Luther, Astelan's dislike of Caliban and Calibanite ways was "well known".Astelan replied that he considered the Lion a taint, that in his opinion everything had gone wrong in the I Legion since the rediscovery of the Legion;s Primarch, and that he would rather serve a more worthy lord, especially one whom he suspected also wished to rid the Legion of the Lion. Astelan dared Luther to say that he intended otherwise, and Luther chose to remain silent.Luther's first act afterward the rebellion against his authority was put down was to agree to promote Astelan's lieutenant, Galedan, to the rank of Chapter Master. Galedan confessed to his former commander that he was pleased that their previous comrade, the conspirator, Melian, had survived, intimating that he would be useful to them when Astelan inevitably attempted to depose Luther as Master of the I Legion. Astelan protested that he had no such plans, for the moment at least. Later, Astelan led a purge of recently arrived Loyalists on Caliban led by Chapter Master Belath, forcing Luther further into treachery and betrayal of the Lion and the Emperor in the process.