Dornsblade

The sword known as the Dornsblade or the Sword of Sebastus, is one of the most revered artefacts by those Space Marine Chapters whom bear the genetic legacy of Primarch Rogal Dorn. The Chapter's Champion that wins the centennial Feast of Blades has the honour of retaining the blade and the solemn duty of presenting it at the next Feast, the contest their Chapter will host, at most, one hundred years later.

History
The simple, resplendent sword known as the Dornsblade can be traced back over ten millennia earlier during the post-penitent Great Scouring following the terrible galactic internecine war known as the Horus Heresy. Rogal Dorn purposely broke the blade he had used aboard Horus' flagship, the Vengeful Spirit when he failed to protect his beloved father and Emperor of Mankind. His second sword, the weapon to which the Imperial Fists and their Successor Chapters refer to as the Sword of Sebastus or the Dornsblade, emerged with the Primarch from the Iron Cage incident on the world of Sebastus IV.

Normally, the greater glory of the wielder of a weapon, the more extravagant the decoration of the weapon wielded. Not so, with the Dornsblade for it was a weapon that bespoke of spartan honesty and rang with history. It entranced the observer with the dull gleam of honours eternally earned. It was rumoured to be unbreakable, a symbolic reminder of the unbreakable spirit of the Imperial Fists in the face of adversity, given form in the trials of the Iron Cage. It also represented Legion unity during the necessities of the Second Founding.

The Dornsblade was crafted from a single piece of high-grade adamantium and remained completely unadorned. Cross guard, hilt and pommel were all bare metal, with the heavy blade counter-balanced by a solid pentagonal prism, with angular edges and featureless faces. The hilt had been cross-hatched and scored to provide a grip, and the cross guard had been stamped with three simple numerals across its breadth: VII, denoting the original VIIth Imperial Fists Legion. The blade was razored and featureless, bar its bronzed discolouration, which was believed to be the stain of the traitor blood that had baptised the blade in Rogal Dorn’s hand, during the Battle of the Iron Cage.

Following the Iron Cage, Rogal Dorn established the tradition known as the Feast of Blades - a centennial competition held between the Imperial Fists and their successors that involved ritual combat between select Chapter champions. This ritual combat was held within a ceremonial arena known as The Cage. Though The Cage is a ceremonial arena it is no dusty amphitheatre, for it is an architectural interpretation of the Iron Cage as far as accounts allow, but the layout is changed between and within each round – going so far as to shifting the geometry of the field during battles.

Through the Feast of Blades, Dorn wanted to strengthen and temper the bonds of brotherhood through contestation between the various Successor Chapters formed during the Second Founding when his Legion was split into separate Chapters. The sole remaining Champion whom was blessed in the eyes of Dorn won the Feast and was formally awarded the Dornsblade as his prize. The Chapter who won this honour was granted custodianship of the sacred blade and the solemn duty of presenting it at the next Fest that they would host, at most, one hundred years later.

Source

 * Legion of the Damned (Novel) by Rob Sanders, pp. 55, 84