A Psyker's reincarnation

Fifteen years had passed since the fateful day on which he entered a new phase of his transformation into a Custodian.

 It could not be said that things were going well for him.

He had initially experienced no significant changes.

He had survived his ordeal and excelled in his subsequent training.

However, this only lasted a short time before it quickly deteriorated when he turned twelve.

When he turned twelve and as the usual changes of puberty took place, he understood how these changes were related to the genetic modifications he had undergone prior to this.

From his understanding, the procedures he went through until this point were as follows.

First, the genetic lock was softened from the age of two to four.

Once this had been achieved, the process of strengthening their constitution and further softening of their genes began. This continued from the age of four to ten.

From the age of ten, they started making real alterations to their bodies, touching upon the very core of their being - their souls - until they were twelve.

By the age of twelve, all the preparatory enhancements would work symbiotically with the natural hormonal changes of male puberty, enhancing and modifying them throughout adolescence to create the body of a Custodes.

That was when his struggle began — a struggle that would last for many years.

When he reached puberty, his experience was vastly different from that of the other candidates.

Until now, he had deliberately rejected the psychic aspect of his transformation.

Unfortunately for him, this psychic force was not just an agent responsible for altering his soul and genes, but the main driving force behind the transformation process in a Custodes.

It seemed that it should have served the role of a guide for how his body should be modified during the process of his puberty. 

This was an issue for him, as he was now lacking the key component of the process that would transform his body as it should have been. 

Even worse, the alien psychic force that was supposed to turn him into a demigod of war was now holding him back because he had not yet managed to get rid of it.

Over the years, the Emperor's psychic force, which he could only contain within himself, had become akin to a weight.

This affected him physically, sapping his strength and making him weaker.

Furthermore, as he had removed the psychic guiding force from his body modification process, his genes soon began to show signs of collapse or uncontrolled mutation.

He now devoted all his time to using his psychic energy to fulfil the role that the Emperor's psychic powers should have played.

This was no easy feat, as he was essentially shooting in the dark, relying purely on deep introspection, instinct, and feedback from his body.

 No matter how hard he tried, it always felt as though a vital component was missing — something that would enable him to truly transcend his human form.

Not only did he have to constantly contain the Emperor's psychic power actively and consciously, or risk being enslaved by it,.

He also had to battle his own physical body, with his genes threatening to collapse continuously.

He could no longer afford to sleep, as even the slightest loss of consciousness would result in his death.

Fortunately, he had developed the ability to partially rest his brain, only allowing the necessary parts to remain active while the rest shut down and recuperated.

Unfortunately, his struggle did not stop there, as the other surviving candidates were all experiencing the normal physical and intellectual growth that their modifications brought. 

He soon realised that he could not keep up with their physical development in any area, whether in terms of height, strength, endurance, reaction time, durability, regenerative capabilities or cognitive ability.

Desperate not to be deemed a failure and disposed of, he managed to learn how to shapeshift using his biomancy making himself appear taller and bigger than he naturally was.

However, it was all a ruse. He was more of an empty shell than the real thing and always came last in physical tests.

He was always on the verge of being eliminated.

 The introduction of targets and goals to be achieved was also new. These revolved around tests of physical prowess, with a leaderboard and cut line.

Those who failed to achieve them were required to make supplementary visits to the laboratory.

He was always among them, but, unlike most of those who received the additional augmentations, he always survived.

From midnight to midnight, they did nothing but physical training and body augmentation, travelling repeatedly between the training area and the laboratory.

Their days were split in half: twelve hours of physical training in the morning, followed by twelve hours in the familiar van.

Despite all this training, he was surprised that they had not yet been taught combat skills or any other military techniques.

But, upon further thought, he realised that there was some logic behind it.

With every new milestone in their physical transformation process, vast numbers of candidates failed to survive, and the process became increasingly severe over time.

 Of the thousands of candidates in his generation, only a few hundred had survived until now.

He had survived until today, but each day had been a struggle.

Each new day had been slightly more challenging than the last, as the parasite's psychic energy inside him had grown stronger and more difficult to control.

It weighed him down, both mentally and physically, dragging him down and sapping his energy.

 He felt he was close to reaching his breaking point, unable to continue fighting against the enormous ball of light inside his mind that was eroding his psychic resistance with its burning heat.

In the absence of a viable solution, he was worried that he would not survive unless he could improve his current situation.

It seemed that the God Emperor had heard his concerns, as an unexpected solution was presented to him.

The outcome would either be the end of his struggle for survival, or his death.