1: The Entering
Every decade or so, the Sagodjour Fjorlag descend in their black thunderhawks to a portion of the Nastrond's hives the tarot drew them. Each one gathers, by force, a hundred youths into its hold and returns to the dark seclusion of the space marine's fortress-monastery, the Doom Chair. Any offending organs are removed from the youth's bodies and their hair is shaved off; their limbs are bound to shackles of incredible weight and they are left to wander the labyrinthine dungeons carved deep beneath Mount Nowhere, beneath the Doom Chair. They will remain down there until madness descends or they escape the dungeons-- and down there they catch whispers of a god, the Praetorian, missing and lost. Those who escape are left to endure the horrors beyond the foggy slopes of Nowhere until they are slain or return weeping to the dungeons.
90 of the first hundred survive.
2: The Milling
The youths must endure a series of punishments, each based on the mortal failings of the individual. A single youth may be chained from the ceiling of a room, a prisoner as he always was and forced to escape before the cell door is forever locked; brothers may be forced to kill each other as they wished to in past life, but now to find the knives and saws lodged under one another's ribs to cut the ever-tightening chains from their wrists. Sometimes one will be forced to decide the fate of his past life companions, but it all leads to one thing: death and the completion of the Milling, through death or no.
3: The Outlast
The mouths of the youths are sewn shut. They are drip-fed every two days and made to repent of the sins of their past life by the reclusam. The shackles are not removed and they are moved to cells deeper and narrower, to the asylum under the Doom Chair where failed Astartes are kept hidden in shame from the rest of the Imperium. There is one exploit within each cell, and the youth must find it; and through blood and pain, he will overcome-- but when he breaks free, he finds there is no real escape, no hope. Even if many were to gather together there would be no hope.
Vorpal, Lord of the Sump beats a lonely patrol throughout the asylums under the Doom Chair. He can smell defeated freedom from anywhere and nothing escapes his eyeless gaze; to complete their next task the youths must escape the touch of his lightning claws and find the apothecarion, where a false sense of security holds them until madness or suicide takes over. And at that point the reclusam draws them back from the edge of insanity-- often a little too late-- and prepares them for the Ingestion.
4: The Ingestion
Their mouths are still closed, and their eyes now are sewn shut. The process begins of implanting the new organs and the hypnotherapy which tricks the body into accepting the strange things. Being the sons of Dorn the betcher's gland does not function; the haemastamen is more often than not dead by the time it is implanted, so is the multi-lung, but they are implanted anyway, for ritual and superstition have risen above practicality and reason.
Wings too; strange feathers may begin to sprout across their bodies, upon their brows and the backs of their hands. Wasted arms may rise from their shoulders or their spines, twitching without control and having no use. If this occurs, the individual is noted down and if the apothecarion thinks it necessary, they may see to the youth at a later stage. The Ingestion is ended after as many years as it needs take with the implanting of the black carapace in a horrible festival called the mass of the holy absorpsion.
5: The Hunting
A dragon is hunted and slain. By every sense other than sight. The youths are each given a combat blade-- which is more often than not a sharpened block of iron or even a tool the apothecary cast out-- and a bolt pistol with a single bolt. Originally the aspirants were transported back to their home planet to find their quarry, but since Nastrond became a dead world they are instead led out beyond Mount Nowhere and given to fight, a genetically modified creature bred in the space hulk which the youths are told is a dragon. They never see them, none see them, so they do not know.
6: The Dripping
The librarius takes over from the reclusam and psychic training begins in earnest. After a year of preparation the youths are removed to the Mind-Forges in the upper spires of the Doom Chair. Suspended in a near-vacuum state, the incapacitated youths are made to fight with the creatures of the warp, released into the mortal plain by the will of the librarians monitoring them. Small creatures at first, malignant imps which caper about and bite; bigger then, everchanging, fleshy things with teeth and beaks and numerous eyes; bigger then, birds with clawing fingers who spit flames-- and then the dead. The spirits of Astartes past rise from their halls of rust and blood and contend with the youth's minds, and every daemon before is nothing compared to the generation dead.
7: The Returning
At the very last, as the initiate finally accepts his doom; he gives up his life for nothing, nothing. The moment he slips from that last crumbling brink of madness, he is caught up and brought back to full health-- his eyes and mouth are torn open and through excessive drug use, in the final two years he suddenly becomes an Astartes as his body changes shape and muscle tone returns to a form it remembered but never had. At the very last, he dons the ancient ochre and black plate of the generation dead, takes up their wargear and march upon his ultimate fate wherever it may be sought-- and, hope beyond hope he may yet find his Primarch.
Out of the hundred youths we followed this last decade, only one survived to the end. He has known darkness and pain few others would dare to know. Some of the uncountable scars plastering his body might pass away but the horror in his mind will never leave his waking eyes-- yet he endures, screaming in triumph atop the great heap of corpses he trampled to find Throne forsook him long ago and fate chose this path for him from the start.
For this reason the Sagodjur Fjorlag are always filled with dismal thoughts. They are sadistic masters of escapology who delight in nothing but the touture of their enemies. Their forte lies in underhive-fighting and hulk-fighting, yet they tend to fight with what appears to be reckless abandon, for fear is naught and death is less, for what concern is theirs in this? Life is nothing to them, be it their own or their allies.