Cal is the undisputed master of the Atropos War Clan, serving in a dual role as his War Clan's master weaponsmith and war leader. He is considered to be a soullessly cold and emotionless figure, made all the more imposing in his hulking black and emerald Power Armour.
During the lamentable internecine conflict between Space Marine Chapters known as the Badab War, Valund Cal and the Sons of Medusa were treated with suspicion by their fellow Loyalists both because of their widespread deviation from the tenets of the Codex Astartes and because of their supposed ulterior motives for their involvement in the conflict.
But they soon put any doubts to rest as to their effectiveness when fighting against the forces of the Secessionists.
Iron Thane Valund Cal is the master of the Atropos War Clan of the Sons of Medusa contingent that took part in the Badab War. Clad in his hulking black metal and emerald armour, it is almost impossible to tell where the man ends and the machine begins.
Vaylund Cal's almost entirely augmetic body is a testament to his lifetime's work as a servant of the Machine God. What little remains of his organic tissue is shot through with bionic and auto-sanguinary systems that increase his strength and endurance beyond even the superhuman levels of a Space Marine.
The Sons of Medusa closely follow the tenets of their Iron Hands forebears, purging the weakness of the flesh with the purity of the machine, and indeed go even further than their progenitors in this regard thanks to the dangers they face as a space-borne Crusading Chapter.
As a fanatic member of the Moirae Sect of the Cult Mechanicus, Cal is renowned for employing Devastator Squads with extremely high levels of deliberate cybernetic augmentation in his clan's forces, skirting to the edge of what some more traditional Astartes see as a heresy against the Emperor's divine order. These squads are deployed in an implacable advance against the enemy, ruthlessly and systematically gunning down their foes.
During the Badab War, the inhuman Valund Cal and the Sons of Medusa were treated with suspicion and barely concealed contempt by their fellow Loyalists for their Chapter's widespread deviation from the tenets of the Codex Astartes and because it was believed by many of their fellow Astartes that they had ulterior and dark motives for their part in the war. The Sons of Medusa joined the Loyalist cause in the Badab War in direct response to Legate Inquisitor Jarndyce Frain's call for Space Marine re-enforcements after the Secession of the Astral Claws had been declared heretical.
The Sons of Medusa's stated reason for participation in the war was the punishment of the Renegade Astral Claws and the other Secessionist Chapters whom they viewed as having earned retribution for their betrayal of the Emperor's trust.
Although Iron Thane Valund Cal deferred to the magister militum (supreme commander) of the Loyalist war effort, Lord High Commander Carab Culln of the Red Scorpions, in strategic deployment and the operational tasking of his Chapter, no Sons of Medusa answered to the orders of any but their own Chapter superiors at the tactical level.
Culln had fought alongside the Sons of Medusa before during the defeat of WAAAGH! Skullcleava thirty years previously and knew them well, whilst the Red Scorpions also earned the Sons of Medusa's respect as a Chapter and this helped to maintain amicable relations within the Loyalist camp.
This prior history allowed Culln and Cal to pursue a smooth working relationship when they might otherwise have been in discord due to their disparate natures, and Culln wisely deployed the Sons of Medusa only where their strengths and tenacity would prove most advantageous to the Loyalist cause.
The Sons of Medusa took part in multiple engagements during the conflict, including the scouring of Cygnax of Secessionist forces as well as leading assault raids against Decabalus and Eshunna, the outer worlds of the Badab Sector.
The Sons of Medusa most famously conducted the subjugation campaign against the rebel world of Galen. The last major engagement the Sons of Medusa took part in was the hard-fought assault on the orbital fortress of Sentinel-Sigma in preparation for the final Loyalist attack on Badab Primaris.
It was Vaylund Cal at the head of the Atropos Terminators who fought his way to the Star Fortress' main engine vaults and severed the five-metre-thick plasma couplings to silence the station's guns, allowing the Loyalists free rein to attack the station's surface. The eventual conquest of Sentinel-Sigma shattered the Badab System's vaunted "Ring of Steel" defences and allowed the final assault on Badab Primaris itself to begin.
- Imperial Armour Volume Ten - The Badab War - Part Two, pp. 98-99, 181
- Forge World - Space Marine Badab War Characters Update Version 2 (6th Edition)