Following his resurrection and prior to the Indomitus Crusade, Roboute Guilliman organised a number of the newly developed Primaris Marines into new Chapters.

Most Ultima Chapters recruited from their own when it came to leadership.  However in this instance due to the uniqueness of the Chapter, Guilliman and Cawl decided that a more experienced and unique hand was required.

Since the Chapter’s gene seed is a unique hybrid and the consequences to them of this are unknown, the decision was made to recruit someone of proven worthiness and pureness of spirit that could guide the Chapter in mastering any flaws that may occur.  Who better shows embodiment of this than the Grey Knights.

A mystery to the rest of the Imperium, knowledge of the Grey Knights was gifted to Cawl shortly after the Second Founding when Guilliman entrusted him with the Sangprimus Portem/Magna Mater.

Rather than choosing from one of the Grey Knight Masters, who were exemplary in their own ways yet had reputations of being rigid and inflexible; Cawl knew a unique individual would be required.  Someone who had faced adversity and the depths of evil and prevailed, and could easily adapt.  After discussions with the Grand Masters of the Brotherhoods, one name was given more than any other - Alaric.  He proved time and time again that he had the pureness of spirit and strength of character to become a powerful leader.  Although he was a great loss to the Grey Knights, they understood why he was needed and even risked the wrath of the Ordo Malleus by allowing him to be taken.

High Exemplar Alaric Silvarius was formerly Brother-Captain Alaric of the Grey Knights; however, he has since undergone painful specialised surgery by Cawl to grant him the extra organs and stature of a Primaris Marine.  He was the first to undergo this procedure and almost died in the process, only Cawl’s exhaustive knowledge of the human form and Alaric’s adamantine mental fortitude and control over his own body saved him.  This procedure became known as the ‘Rubicon Primaris’ and to cross this is to elevate to another level of post-human existence.

In his previous life as a Grey Knight Justicar, Alaric distinguished himself with his banishment of the Greater Daemon Ghargatuloth on Volcanis Ultor in 999 M41, the Daemon controlled Castigator Titan on Chaeroneia and as one of the only Space Marines ever to return from the Eye of Terror alive and untainted.

On returning from the Eye, Alaric underwent years of stringent physical and spiritual testing by the Grey Knights and the Inquisition.  Eventually he was declared pure by the Grey Knights and Ordo Malleus and given the full rank of Brother-Captain.  He then continued in this position with the Grey Knights for some time until Cawl and Guilliman inducted him early in 5.M42