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|Space Marine (Novel)
D'Arquebus was born on the Hive World of Necromunda in Hive Trazior. D'Arquebus came from a comparatively wealthy family: his father served as Calculator Maximus to Lord Spinoza - a clan leader whose family owned many factories in the lower habs. Lexandro was a member of a Brat Gang called the Lordly Phantasms, a group of upper-hab youths who delighted in using their exotic weapons and equipment to terrorise lower-hab gangs.[1a]
At the age of fourteen, after his father's "financial irregularities" had toppled his family from their favoured position, d'Arquebus applied to join the PDF with the further hope of possibly being transferred to the Imperial Guard.[1a]
Unknown to d'Arquebus, these interviews were being observed by Sergeant Huzzi Rork — a recruiter for the Imperial Fists. Rork took an interest in d'Arquebus and ordered further test to measure his physical, mental and psychic capabilities. Following this, Rork offered d'Arquebus the opportunity to attempt join the Imperial Fists. D'Arquebus, along with fellow Trazior-hivers Biff Tundrish and Yeremi Valence, was then transported from his homeworld to the Imperial Fists' mobile Fortress Monastery, the Phalanx.[1b]
Career in the Scout Company
Once aboard the Phalanx, the recruits were inducted into the 10th Company and began their regime of training, surgery and initiation into the Chapter. During this process d'Arquebus, Tundrish, Valence and fellow initiate Omar Akbar were formed together as a Scout Squad under the command of Sergeant Zed Juron. The scouts fought in several campaigns including a notable engagement on the world of Karkason where the lone scout squad commandeered a rebel Titan by eating the brains of the Titan's crew and absorbing their skills through their Omophagea organs. The squad utilised the captured Titan to maul the rebel forces, ejecting before the Titan's destruction - although with the loss of Cadet Akbar.[1c] After the campaign on Karkason, the surviving scouts were Implanted with the Black Carapace and were inducted as full Battle Brothers of the Imperial Fists.[1d]
Career as a Full Battle-Brother
As a full battle-brother, d'Arquebus served in a squad under Sgt Huron alongside Valence and Tundrish. After at least a decade's active service, the squad was involved in an assault on a Tyranid vessel of Hive Fleet Kraken. D'Arquebus survived this engagement but his brothers Tundrish and Valence were killed during the assault.[1e] In order to overcome the grief of their death, he removed the flesh from his hand and scrimshawed the names "Biff Tundrish" and "Yeremi Valence" on his bare bones along with the words "Necromunda" and "Hive Trazior." The flesh on the hand was later replaced.[1f]
Involvement in the Inquisition Wars
D'Arquebus eventually rose to the position of Captain. It was during his tenure as Captain that he met Inquisitor Jaq Draco. Captain d'Arquebus then joined the Inquisitor's group in their attempt to infiltrate the Eldar Black Library of Chaos and steal the fabled Book of Rhana Dandra.
Harlequin was at one point republished as part of the Inquisition War Trilogy which was rewritten to expunge previously non-canon material (for instance, the character of Grimm is changed from a Squat into a human Tech Priest).
When Space Marine was republished, the decision was made not to ret-con the material. On this issue, the publisher stated:"Although the temptation was great to rewrite significant portions of this book to make it conform to current background, as a curiosity piece, an historical snapshot of the Warhammer 40,000 universe circa the early 1990s, this book is invaluable." 
Forge World has included an emblem with the name "Lexandro" as part of its Imperial Fists brass etch, a nod towards including the character in contemporary canon.
- 1: Space Marine (Novel):
- 2: Harlequin (Novel), [Needs Citation]
- 3:  (link no longer functional)
- 4: Index Astartes II, [Needs Citation]
- 5: Forge World's Imperial Fists Brass Etch (link no longer functional)
- Chaos Child (Novel) by Ian Watson