Aeonid Thiel was a Sergeant of the Ultramarines 13th Chapter, 135th Company, who distinguished himself during the Battle of Calth for his adaptability and unorthodox thinking.[1a]
It was customary for the Ultramarines to develop "theoreticals" for both personal and tactical combat, against all manner of xenos or human foes. Thiel, however, was marked for censure by his superiors for theorizing combats between Space Marines. His superiors felt that this scenario was both impossible and bordering on treasonous, but Thiel defended his reasoning, saying that Space Marines were the galaxy's most formidable warriors, and it was good sense to analyze their strengths and weaknesses as thoroughly as any other opponents'.[1d]
Thiel's superiors were not convinced, and he was sent to the flagship Macragge's Honour to be rebuked by Chapter Master Antoli, and possibly by Primarch Guilliman himself. While waiting for his superiors, he decided he was already in as much trouble as he could be, and spent his time practicing with the exotic melee weapons from Guilliman's private collection.[1b][1c] When the Word Bearers unleashed their traitorous attack, the Macragge's Honour was invaded by a horde of daemons summoned from the Warp. Thiel quickly discovered that the daemons were more vulnerable to fire and melee weapons than traditional firearms. He fought his way to the bridge, where he saved Chapter Master Marius Gage's life from another daemon.[1d]
Thiel explained to Gage his thesis that, in a battle between former brothers, the Ultramarines' greatest weakness was their predictability, while the Word Bearers' greatest advantage was the shock of their betrayal; the only way for the Ultramarines to regain the initiative would be to dispense with both - using unorthodox tactics and strategy and wage war against their former brethren with all ferocity. Gage quickly approved of Thiel's logic, and detailed him to lead the parties of Ultramarines to scour the remaining daemons from the ship.[1d]
Thiel was later one of the party of fifty Ultramarines who accompanied Guilliman aboard the orbital weapons platform occupied by Kor Phaeron and his elite guard, the Gal Vorbak.[1f] Thiel fought bravely, but was unable to prevent Kor Phaeron escaping.[1g][1h] Thiel would later return to Calth as part of a relief effort and spent many years fighting the Word Bearers.
Later, Thiel sought an audience with Gulliman, hoping to brief him on the situation on Calth. Gulliman eagerly agreed, for he valued Theil honesty and directly-to-the-point attitude. During their audience, Thiel asked if Gulliman would mind meeting his squad, all 'orphans' from previously destroyed squads on Calth who had banded together under Thiel. Again, Gulliman agreed. This would almost cost the Primarch his life as Thiel and his men revealed themselves to be Alpha Legion assassins and shot Gulliman at point blank range with their bolters, though the Primarch managed to kill of of them before collapsing. A subsequent investigation was unable to determine if this had been the 'official' Thiel and his squad, or if the assassins had simply assumed their identities on route to Macragge.
Meanwhile, the real Thiel led a squad of red-marked to Iax alongside new Ultramarines recruits to investigate a Promethium rig that had gone silent. Upon approaching the rig their Thunderhawk was shot down, and upon entering the facility they discovered that it was abandoned. After fighting through security Servitors, the group came across a single comatose survivor, who quickly died despite the best efforts of the Ultramarines Apothecary. Thiel and his squad continued to search the rig, coming across a Tech-Priest who explained that the crew went mad and flooded the entire station. Thiel was then assailed by a traitorous Space Marine wielding sorcerous powers. Thiel was overpowered, but saved by his squad. The traitor identified himself as Alpharius and said the word "Nightfane" before he died. Thiel and his forces decided that Iax had been infiltrated by traitors.
Aeonid Thiel survived the Horus Heresy, becoming the Captain of the 2nd Company of the Ultramarines Chapter. He took part in the Battle of Thessala, during which Roboute Guilliman was mortally wounded by Fulgrim. His ultimate fate is still unknown.
At the time of the Great Crusade, it was customary for Ultramarines marked out for censure to bear red markings on their helmets.[1c] During the Battle of Calth, Guilliman ordered that the squad leaders accompanying him aboard the orbital platform paint their helmets red; because the Word Bearers' attack had shredded the Ultramarines' normal command hierarchy and unit organization, and because vox communication was unreliable, Guilliman wanted clear, visual cues for the Ultramarines to follow. Furthermore, he added that after Thiel's heroism of the day, red markings would be badges of honour, instead of censure.[1e]
Immediately after the Battle of Calth, it became customary for Sergeants of the Ultramarines, to paint their helmets red to signify their rank, including those of the force led by Captain Ventanus during the Underworld War. The tradition has endured in the ten thousand years since the Heresy, among the Ultramarines and several Codex Chapters.
- 1: Know No Fear (Novel)
- 1a: Dramatis Personae
- 1b: Target//Acquisition, Chapter Four, pgs. 51–53
- 1c: Target//Acquisition, Chapter Eight, pgs. 93–95
- 1d: Target//Engagement, Chapter Four, pgs. 243–48
- 1e: Ushkul/Thu, Chapter Two, pg. 351
- 1f: Ruin//Storm, Chapter One, pg. 368
- 1g: Ruin//Storm, Chapter Three, pgs. 384–385
- 1h: Ruin//Storm, Chapter Four, pgs. 392–393, 396
- 2: Calth That Was (Novella), [Needs Citation]
- 3: Censure (Short Story) - Legacies of Betrayal (Anthology)
- 4: The Unremembered Empire (Novel), Chapter 5
- 5: Codex: Space Marines (5th Edition), pgs. 21, 113
- 6: Dark Imperium (Novel), Chapter One
- 7: Nightfane (Audio Drama)