Regardless of lineage, honour and title not all of those set to inherit the seat of ultimate power get to do so. Not all pilots can bond with their machines of war. The strain of the neural interface with the machine spirit of such a construct to much to bare.
Not all is lost for these individuals, a Knight Household has many other a function to undertake.
Such was the story of Lord Black, the eldest son of Ignatious Black and next in line to the throne of the God Machine 'Implausible Victory'. An ancient knight, honour laiden and battle served no finer machine could have awaited the eager youth. It was however, not so. The Machine Spirit rejected him, violently. The young Lord Black had to be carried away, the stain on his honour would live forever.
Stains however, fade with time and in the 41st Millennium honour is a somewhat malleable.
The young Lord still was given an knighthood purely as an homourific title and then was trained by the finest Adepts of The Mechanicum and House Black in the arts and rituals needed to keep the omnipotent machines functioning.
This Ser Black did for many decades, that is until his body eventually began to fail him. Despite the efforts of all the Apothecaries in the system Ser Black would soon be dead. In the coming weeks Black became a bitter and spiteful being, and slowly he turned this emnity toward the God Machines of his house. Powerless against them and their pilots Ser Black prayed for the strength to live, his desire to see his house burn was all he had left.
His prayers were answered.
Ser Black took a squire and formal envoy on what he called a 'Pilgrimage' to further the House's knowledge of the constructs of War. The true meaning of Black's Pilgrimage was to track down a former adept of his House the previous Tech Priest had seen banished for what he had called Tech Heresy. Black had later learned what the young adept had attempted was a means to shackle and ensalve the Knights machine spirit and allow the pilot a greater comtrol. Black saw little wrong with this and wanted to speak the young man out to try and gleam a portion of his wisdom that may prolong his life.
As the envoy was forced marched across vast plains, through dense forests and across mountain ranges it became evident Ser Black cared little for the envoy. At who fell were left where they fell, any who attempted to leave were treated a deserters and executed and when supplies became scarce those left became sustenance.
Many months later and near death Ser Black, carried by his squire had been pointed to a remote hovel on the brink of a forest. They stumbled through the shack's door into an empty room. Knowing he could not go on Ser Black spat the darkest curse against The Emperor and vowed he would see his soul serve the ruinious powers in hopes he would watch him die.
Just before his last breath left his lungs he heard a harsh mechanical rasp whispering hope.
Black cared not for the conditions nor price, he would live.
A mixture of Heretical chants, the darkest sciences and rites of pure evil gave life to Ser Kuro, now more machine than man and his soul consigned to the ruinious powers but live he did.
The squire reeled in horror at his master's new form but it did hi little good, for his fate was inextricably linked, he was to be the price for Ser Black' longevity.
Ser Black however did not wish to pay for his new form, Ser Black was a Knight and as such should not have to pay this peasant for saving him, instead he waited for the Dark Adept to complete his experiments, allowed him to improve the poor Squire, then in a single moment of darket clarity, offered the Adepts life to his new gods.
Now sealed into his armour, his will slaved to whoever held a command wand, squire was now a mechanical abomination designed purely to protect his Master. Ser Back had to have him. Ser Black stole the command wand and had squire perform the sacrifice. In return, Black was permitted to keep the Squire and gifted with all the Adepts darkest secrets.
The pair now serve Inquisitor Heliosz in exchange for bio samples for the now named Ser Kuro's experiments.