Tai gave the unconscious Fenrir to his pack of wolves as they all entered the apartment room located in a pocket dimension.

"Thank you for this, Fenrir's master," Hauser said, howling at Tai to show respect.

Tai nodded, smiling. "No problem. By the way, 'Fenrir's master is too long. Just call me Tai."

Hauser nodded and went into the room as the entrance to the pocket dimension disappeared.

Since it was getting late, Tai decided to get himself his own room, and since he didn't have high expectations for a room, plus the fact that it was only him, the apartment was very cheap with the reason that the price was somewhat high was because of the pocket dimension feature.

He entered his apartment which consisted of 1 bedroom, 1 bathroom, 1 living room, 1 kitchen, 1 dining room, and 1 laundry room. Every room was perfectly furnished meaning Tai didn't have to bother with buying furniture, but it did cost extra.

His clothes morphed into a soft material since it was made of darkness as he laid down on his bed. As he was laying down, he asked Nagi a question, "Nagi, how do I completely merge with my darkness? Become one with the void so to say."

"Oh, well that's easy, master. Do the same thing that you did with your heart, but only this time, do it with every part of your body. Be careful though, as this isn't an easy task. The 'element' of darkness has a will of its own, different from mine meaning that I can't control it. During this process of remaking your body out of darkness, it will try to take control of your body. I guarantee that this also happened to your sister and fortunately, her body did not get taken over."

"Hmm, interesting. Well, let's try it out now." Tai was familiar with making a body part out of darkness. He had already done it when his heart had been destroyed causing him to partially merge with his darkness, but not completely, so he was pretty confident that he could do it. No, he had to do it since if he failed, the darkness would consume him and that was bye-bye Tai.

So do I just destroy my own body and remake it with darkness basically?

Trying out his plan which sounded crazy since he was willingly destroying his own body, Tai used his darkness to destroy his bones, remaking them with his darkness and forcing his body to use the new bones that were made of darkness.

This process would usually be very painful, as destroying ones own body wasn't exactly the most relaxing feeling, but thanks to his Pain Immunity skill, he could ignore all of the pain and concentrate on blocking the darkness that was trying to invade his mind.

At first, as Tai replaced a few of his bones with darkness, nothing unusual was happening, but as more and more of his bones got replaced, he could feel a deeper entity, one that originated from the void start breaching his mind's defense.

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His intelligence stat which he has invested quite a bit of his stat points in were acting as a layer of defense, slowing down the attack of the entity, but the defense wasn't invincible. It slowly but surely crumbled as Tai fully replaced his skeleton with one that was made of darkness and moved onto his muscles. 

Tai decided that he would get the easy ones out of the way first: Bones > Muscles > Skin > Nerves > Then other important parts that required a bit more concentration.

The reptilian entity that had helped Tai a bit was watching him, wondering if he would be able to completely merge with the void of darkness and not get corrupted in the process.

"Ș̜u͍̯̘̭͕̗̼c̥̪̗͟ͅc̤͓͎̻̰̠̜u͚̰͈̬̫̞̳m̢b̢̫̩̗ ͚̩͔̥t͏o̲ ̢͙̖̤͇̣̻t̞͓͕h̝e̛͉̱͔̬͕ ̲v̫͎̙̯̦̬o̷i̡̟̠d̡͎," the entity said, breaching Tai's last layers of defense as it started attacking his mind.

Tai let out a groan as he fought back against the entity's advances. "You are my tool, not the reverse!"

The entity laughed. "Y̧̼͕ọu̜͉͖ ̼̬̥̫t̹̜̼̙h̴̝i̟̝ǹ̹k͖̘͚̣̲͓͖͟ ̺͎͍͓̤͙̹y̛̮o̝͈̫̤̝̱ͅu͜ ̢̗̺̲͉͇a̙̦̦r̶͙̺̪̯͉̩e̷̙̭͕ ̸͖̰t̷̺͓̺h̫̳͓̞͈́e̩̤̯͘ ̨̰f̘̦͓̻̫i̵̙̺̪͍͙̗̗r̠͚̩͈͍̯̭s̷̞̞̣t̨͕̣̺̝ ̧̘͎̞̲̤t̗̟̙̘o͚̗̹͈̯̝͔ ̵̗̤t̛̗͕͙̣̯͚ͅh͕̣̯̯i͟n̦̗ͅḱ̹̮̫̱͎̖̪ ͏̺̬̘o̴̬̣f͈̺̼̥̮̺̲̀ t̗͇r͈͍̘y̠̹i̶͙̭͎̪͚̦ṉ͖͖͕g̵͙̙̺̺̰̯ t̮o̜̣̬ ̞͍͎̱̪͞u̟̬̼̠̬ͅs̶e͡ ̞̼͡ṱh̯͖̣͢ͅe̠̪̹͍͜ ͍̦̻͔͡v̢o͏i̸̺͍d̨͖̝ͅ?̙̹̮̭̲̯ ̢͉͎͍̞̠̣M͉a̙̳̪͢n҉̖̥̞y̢̠͎̳̙͖̰ ̷ha̺͙v̦è̥̙ ̗͉͇̝͇̠c̴͖̪͖̙o͏͍̭̳̰̩̝ͅm̠e͈̬̹̦̠ ̙̜̝b͕̪͕ͅe̙f̭̲͈̖̞̗̭o̢̯̠̩͈r̭e͓̞̮͞ ̨͔̫ͅy͝o̺̹̠̖̘̯u̵̱̱̙̲̝͓̤,͡ a̜̜̭̪͙̰n̙͎̭d̢͉͇̫͎͈̯ ̫̞̤͎̝̜͖m̩̜a̷̦̺͍͉n̡͕̱̳͖y͇̖ ̺̺̮̕o̮͓͚̼͔͘f̢̯̬̱̝̠̪ t̴h̩̣̲͕̀e̪̱͇̳̪̘̰̕m̷͎͉̺ ̧͕̹̜h͏̟̥̰̗̬̪ͅa̤̱̭͟v͟e̢͎ͅ ̠̬̤͎̲͜ͅͅf͈a͙̲̖̹l͚͎̰̹̩ĺ̠͇̳e͇̱̬̲̗ͅn͉͕ ͅͅu͔̝̫̮̠̠͇n̨̞̫͎̥͕͎d̸e̠̲͓̮̫̳͟r̸̖͍ ̰̱̫̣͖̣̺m̜y̢ ̴͍̩͉c̶͇̹͙̜̪ơ̻̻̮n͓̮̪͓̖̖͞t̗̣͙̯͙͈r̮̠̻ͅo̱͟l̮̥̞̠̝͉̲̕."

"Well, I am not like those that came under your control. I am Tai Zenith!" Tai finished converting his muscles and started working on his nerves, skipping the skin to do it later.

With a lot of his body converted into darkness, the entity had become stronger and was slowly but surely invading Tai's mind. Tai did his best to fight back against the invasion of his mind, but all he could do was slow it down and hope for the best.

Am I missing something? If I keep going how things are going, then my mind will get taken over.

Shaking his head, he decided to just continue with the transformation and worry about it later as he moved from his nerves to his internal organs. This part was arguably the hardest, but that was only because the user doing the process were supposed to experience the extreme pain that came with destroying one's own organs along with trying to hold back the invasion of the entity.

This would normally be the case, but since Tai was immune to pain, all he had to do was concentrate a bit harder and deal with the entity's invasion.

After a few minutes, Tai had finished converting his internal organs like his lungs, stomach, brain, etc to darkness and now came the easiest part, converting his skin, and he would be fully merged with his darkness.

Now, while this might be the easiest part of the process, the invasion of the entity made it incredibly hard so. The entity was constantly unleashing barrages of mental attacks that Tai did his best to defend against, but this wasn't Tai's strong suit. He was a much more physical fighter, and wasn't the best with 'magical tasks', but he could do them decent enough to hold up against the entity.

Once again, though, no matter what he did or how he defended, the entity was still chipping away at his defenses seemingly with unlimited stamina.

"Come on... Just a little... bit more..."

As Tai converted the last pieces of his skin and body, his eyes and entire body turned pitch black, and the entity took control of his mind.

Tai didn't do anything wrong. It was just inevitable. To become one with darkness, one must first be controlled by it and then it is up to the person if they can take back the control of their body.