Feeling the new chakra clashing with the already existing one Saito started harmonizing the two natural chakra's slowly fusing them. It took a great deal of will and control to fuse the two senjutsu chakra types slowly he started overpowering the erosion of the wood type chakra, Slowly the process of fusion became easier when he fused about half of the senjutsu chakra, he suddenly lost control, the fusion accelerated at crazy rate, soon the wood type chakra was fully assimilated but the natural chakra kept getting more concentrated.
Saito started panicking if he couldn't regain control he will die. Karin who was observing Saito didn't feel anything even while using her seals to monitor Saito's condition, she felt the Biju chakra disappearing but for some reason Saito was still in deep meditation.
Meanwhile Saito finally managed to regain some control, but just as he was about to relax, he felt a strong oppressive force, and soon he found himself in a black space, as far as he could see he was in a void, nothing existed there, he tried using his abilities but no matter how much he tried he couldn't move his chakra, in fact he didn't have any chakra in his body. Helpless Saito started walking around, he knew that panicking won't do him any good, so he started walking looking for a way out. He tried checking his stats only to be met with silence, he knew that he didn't die otherwise the wheel would have summoned him, so he could only keep looking for a way out.
Karin started panicking, at first Saito seemed stable but suddenly he started floating about five meters above ground, she didn't know what to do she couldn't feel any chakra been used and Saito's own chakra signal was slowly shrinking, and just as Karin was going to try waking him up, the chakra stopped shrinking leaving only a meager amount, but before she could move another strange thing happened, Saito's body started changing, he was slowly changing into a wood sculpture. Helpless she sent a message to Tsunade, soon Tsunade entered and started observing Saito's condition, Tsunade while she didn't master sage mode she had a good idea about the principle, luckily Saito didn't transform fully into a statue, she could still feel a small amount of vitality, and his clones where still meditating absorbing natural chakra, she tried waking them but to no avail. She didn't dare to destroy the clones.
Having no idea to save Saito, she ordered an Anbu team to guard the place, while she contacted Jiraya in order for him to come and check Saito's condition. Karin calmed down and started looking into the Uzumaki records for any information about Saito's situation, she didn't want to tell the others about Saito's situation, and they still had to be on guard against the Akatsuki, in case they made a move.
While Karin and Tsunade were looking for a way to help Saito, he was still in that dark space, he didn't know how much time passed but he knew that he won't be able to find an exit by walking around aimlessly. To his surprise he didn't feel hungry or tiered, with nothing to do he sat down, emptying his mind from all stray thoughts, he started meditating. He didn't have chakra but he could still calm his mind and try feeling his surroundings.
Saito didn't know how much time passed he was meditating for a very long time, he didn't feel anything, but he instinctively knew that this was the right path. After about a month passed, with him still meditating he suddenly felt a presence. It was familiar, at first it was weak but soon it grew stronger, opening his closed eyes, Saito saw a horrifying sight, the world was no longer a dark void, he was standing in what looked like a battlefield. Everywhere he looks, he sees mutilated bodies, ranging from children, women and elderly. In the middle of the chaotic scene a man was standing.
As if sensing Saito looking at him he turned his head, standing face to face to Saito.
Saito: "Who are you? No! What are you?"
Man: "I'm you."
The man standing in front of Saito was a perfect copy. And for some reason Saito knew that after this encounter only one of them will survive. Without saying a single word the doppelganger's body became red and began emitting steam. Saito recognized that technique, medical chakra mode, before he could react his opponent disappeared from his place appearing directly in front of him sending a barrage of attacks at him.
Saito could barely block some attacks his body was strong but he didn't have chakra so he didn't have access to any of his abilities. He knew he was at a huge disadvantage he could only hold on while trying to find an opportunity to counter.
For what seemed like an eternity Saito's doppelganger kept assaulting him, Saito managed to land some attacks but the damage was negated due to the chakra mode. He was desperate, his body was aching from all the attacks, and he couldn't heal himself so the damage kept piling up, if he doesn't find a way to counter attack or at least heal he will die.
He had an actual theory about the place he was stuck in, from his observation this place should be inside his soul, and because this place is basically his territory he should have the power to manipulate it. While dodging some of the attacks and receiving a dozen, he felt it finally the chakra that was inaccessible. After gaining chakra he started pushing back, healing his body all while countering the attacks, after numerous exchanged he finally managed to kill the doppelganger. Just as he was about to let out a sigh of relief, the supposedly dead doppelganger started trashing around and soon he stood up, this time the pressure he emanated was stronger, his body no longer gave of steam but his body gave off a dangerous aura.
Saito: "Oh my god again!"
Saito also activated his third phase chakra mode opening all gates up to the seventh, he started again clashing with the doppelganger. Surprisingly this time he was the one being pushed back, unlike the first time the doppelganger was using chakra sword and advanced Taijutsu attacks to their fullest potential, and Saito was still tired from his first battle, but he still persisted.
After numerous clashes Saito decided to take a desperate measure, he never had the courage to use it but now he felt that he could no longer hold back.
Saito: "I hope, I won't regret this!"
Without any hesitation he activated the eighth gate, his power rose to a freakish level. And to his surprise he didn't feel the strong backlash he expected. He felt as if he finally managed to complete a puzzle. His next attack directly obliterated the doppelganger, but this time he didn't let his guard down, he started observing his surroundings, and just as he expected another Doppelganger appeared and to his surprise two others appeared, using the eighth gate gave him enormous power but it also drained his stamina and chakra at a crazy fast pace. Each one of the Doppelgangers entered an elemental sage mode with the main one using Wood sage mode.
Saito: "Is this some kind of test?"
System: "Yes, You have achieved something that was never done before, fusing two natural chakra types, this opened a new possibility for you to understand a universal law, if you manage to pass this trial you will gain immense power."
Saito was already fighting his clones, even using his perfected third phase he was being pushed back, mostly due to the Wood sage clone, that restored any damage it received or the two others received.
Saito: "But why didn't, I have access to my stats earlier?"
System: "It was deemed necessary that you had to be alone in order for you to concentrate on sensing your surroundings."
Saito: "So is there a way for me to clear this trial or is it going to keep going like this."
The System didn't respond to him, Saito for now could only concentrate hard on fighting the clones in front of him. He knew that he couldn't keep fighting this way ore he would be killed.