Author notes: sorry for the misinformation, I just found out that having Mangekyou Sharingan doesn't grant the user Amaterasu and Tsukuyomi. Therefore, Madara and Obito will no longer have those two abilities from this chapter.
Two days later, World Serpent's headquarters
Inside the throne room of the mysterious organization, there were two men who were having tea at opposite positions to each other. One was the Sire and the other one was his mentor. No need to say, the duo was none other than Madara and Obito. They were having a discussion about recent developments in World Serpent and themselves as well.
"So you have discovered your own Rinnegan ability?" Madara took another slip of tea while expressing his interest in this matter. He obviously was curious when Obito brought up this topic.
"Yeah, It's a space-time technique," Obito answered.
"Another one, huh? You're too lucky, Obito. First is Kamui and now that one. Life is so unfair! Anyways, how did you discover it?"
"Well, I coincidentally found my Rinnegan ability during the last battle..." Obito hesitated, not wanting to reveal the truth behind it.
"Bring it on!" Madara encouraged him while jewing a cookie.
"I had to use Izanagi to win that fight." Obito spoke falteringly.
"Izanagi!?" Madara exclaimed in surprise. But he later calmed down after realizing his partner's Sharingan was still sighted. It was no longer a concern since Obito somehow had avoided the consequence of using said forbidden Jutsu. After a few seconds, Madara finally came to his conclusion with all details mentioned by Obito.
"Now let me guess. First, you say it's a space-time technique. Second, despite using Izanagi in the previous battle, you've gotten rid of the blindness. Those two reasons lead me to a possibility: Your Rinnegan ability allows you to manipulate the time flow of an object. You rewound your blind Sharingan back to the point before you used Izanagi. Am I correct?"
"As expected of Madara, you are truly a genius in combat analysis! I just revealed some details and you immediately know my Rinnegan ability - Takeminakata. Indeed! That's what my left eye is capable of." Obito told his partner as he confirmed Madara's guess was right. In addition to that, he also shared with Madara his recent discovery of Rinnegan in this world.
"By the way, I also discovered that the Preta Path can absorb Honkai energy. I tried it on a Honkai beast in the last encounter and succeeded. In this process, Honkai energy can be transferred into Chakra and added to my reserves."
All of a sudden, two Uchihas were dazzled for a brief moment. When their visions returned, the scenery of the throne room had changed into an entirely different place. They found themselves in another dimension ruled by an omnipotent entity.
In An Unknown Dimension
At the moment, they were in the presence of the Otsutsuki God. Madara did not seem to be surprised since the Uchiha had encountered him before. However, Obito was a different story, astonished as he beheld an unbelievable scene.
There was a behemoth humanoid avatar, possessing blue skin with straight white lines running down the whole body. Other than that, he had three light blue eyes, two eyes on the sides and one on the forehead. Moreover, the masked Uchiha felt nervous because of the space surrounding them. There were countless widened light blue eyes staring at him from all sides. When he was about to escape this freakish realm with Kamui, a powerful voice spoke up.
"Don't leave this soon or you will regret it, Obito Uchiha. I want to meet Madara and you for a reason."
"Huh!? How do you know my name?" Obito got stunned, not expecting his identity to be known by a stranger. Behind the mask, the Uchiha was sweating from anxiety. He then turned to have a look at Madara's expression. To his surprise, the fellow Uchiha showed no worry. In fact, his partner made a smug smile on his face.
"I'm an Otsutsuki like who you know as the Sage of Six Paths." The god-like entity revealed himself to the two Uchihas. Although Madara had somewhat guessed his identity when he mentioned him as a descendant of his fellow, this truth still got him in shock.
"After hundreds of millions of years absorbing natural energy from billion planets, I have evolved to an omnipotent God beyond all beings and understanding. However, the price of becoming a supreme being was great as well. I lost my physical body and was imprisoned within this realm forever." The Otsutsuki God told them. After the explanation was finished, he looked down at them and questioned.
"Since we don't have much time left for this conversation, ask me any questions you want. I'm sure you already have some in your mind, right?" As he expected, Madara was the first person to raise his voice and told him about his doubt.
"Yes, I'm having a problem with my visual prowess. My Genjutsu doesn't work on certain enemies."
"First was the giant octopus-like Honkai Beast that Obito and I defeated in Tokyo. I thought it was a normal thing since the Will of Honkai was controlling that monster. However, the second case was totally different. A Schicksal Valkyrie named Durandal somehow could break out of my Genjutsu like it was nothing." Madara described his trouble to the Otsutsuki God. After a moment of silence, the ancient Otsutsuki entity eventually responded to him.
"Indeed, your conjecture on that Honkai Beast case is totally founded. More or less, all Honkai beings are under the Will of Honkai's influence. Thus, the fact that the Honkai Beast was immune to your Genjutsu is normal. However, in the case of the Valkyrie you called Durandal, perhaps she was already possessed by something that could resist your Genjutsu."
"What makes you think so?" Obito questioned and also joined the chat.
"Technically, Chakra is a form of life energy. Therefore, all creatures in that universe possess it too. When the Chakra flow of the cerebral nervous system is attacked by Genjutsu, the victim's five senses are affected as well and thus caused to have illusions. It will be extremely hard to get rid of Genjutsu unless having interference from another force." The Otsutsuki God explained the knowledge in detail to them. The two Uchihas finally were satisfied with the answers they received.
"Moving to the next question, why Honkai energy doesn't affect Madara and me?" This time, Obito was the one to pose a question to The Otsutsuki God. Although Madara did not speak up, he had the same question in his mind. He noticed ever since they came to this world, they had confronted multiple Honkai enemies. Yet, exposure to the high amount of Honkai radiation had not killed nor turned them into zombies. In fact, neither of them experienced any symptoms of the thing called "Honkai Sickness".
"Compared to other species, the Otsutsuki is a superior and special race. Among the multiverse, we're the only exception that is completely immune to Honkai corruption. We never face any physical or mental illness relating to Honkai energy. And as descendants of Hagoromo Otsutsuki, Madara and you obviously inherit that genetic traits. Thus, exposure to Honkai radiation will have no effect on you two." The truth about the Otsutsuki race got Madara and Obito in astonishment. They never thought their bloodline was that special. Being the descendants of the Sage of Six Paths was indeed a favor for them.
"Do you have any guides for us to defeat the Honkai?" Madara asked the Otsutsuki God straight away. Up to this moment, they just had killed one Herrscher only and there were 13 more to deal with.
"Fighting Herrschers by yourself is not a smart way. As I told you before, use Herrscher against Herrscher. I have provided you with the idea, and now your job is to create a complete plan based on it. You have to figure it out yourself."
"How's about Project Stigma? It's the plan which World Serpent is following." Madara also questioned him about the mysterious plan of said organization. Due to the vague description of it in the codex, he had no idea how it worked. But right before the Otsutsuki God could reveal anything more to them, the connection between them suddenly became unstable to maintain.
"When the time comes, you will know about it-" His avatar eventually faded away, making Madara and Obito return to reality.
After a while
"Then I'll do this mission. Take care of yourself, Madara." Obito said to his fellow before leaving the throne room. After closing the door behind him, the Uchiha turned back just to see Raven standing against the wall.
"There's something that I want you to help me with, Ghost." Raven confessed. "Or should I call you by your name, Obito Uchiha?"
Seeing that his identity had been revealed, Obito was forced to accept her request. Needless to say, he had known who was the one responsible for his information leak.
"Damn you, Madara! You're gonna pay for that"
"Well then, let's talk about it in a private place." Obito then brought her along with him into the Kamui dimension. He did not want anyone to eavesdrop on his business, especially Gray Serpent.
Within Kamui Dimension
Raven was surprised when she was sucked into this realm by Ghost. The place itself is quite bizarre, a dark void of randomly arranged and various-sized rectangular blocks. However, she currently had another concern which was more important than this odd realm.
"So what do you want me to do?" Obito spoke up in a low tone voice.
"It relates to the Rinne Serum that lord Madara injected into me two days ago," Raven responded while closing her eyes. "When I woke up this morning, this thing happened..." Raven opened her eyes again, showing a pair of 1-tomoe Sharingan to her colleague.
"Can you tell me all abilities of these eyes?"
"Those eyes are called Sharingan, a bloodline limit belonging to the Uchiha clan. It seems that the Rinne Serum has granted you my clan's power." Obito said. "But your Sharingan is just in their first stage, 1 tomoe. Most of the base abilities are still locked until your eyes got 3 tomoe."
"What are the base abilities of Sharingan?" Raven questioned.
"There are two main abilities: Enhanced Vision and Genjutsu. With enhanced vision, you can see the life force of others, track very fast movements, predict the next moves, or even mimic them perfectly. The ability also gives you ultimate long-range sight, which regular eyes can not."
"That sounds incredible!" Raven gasped in surprise after hearing such powers. She totally did not expect to hear that. She then asked Obito about the second ability. "How's about Genjutsu?"
"Genjutsu literally means illusionary technique. You can cast Genjutsu on your enemies, trapping them in an illusion you create. However, those with stronger visual prowess can resist your Genjutsu and trap you in their one, keep that in mind."
"I recall lord Madara mentioned Mangekyou Sharingan while telling me about your backstory. So are there any differences between Mangekyou and normal Sharingan?" She asked him about Mangekyou Sharingan in curiosity.
"Of course, there are. A Mangekyou Sharingan is distinguished from a normal Sharingan by its appearance, which changes the form of the tomoe seal. Besides, it grants a unique ability to each user. Mine is Kamui which allows me to manipulate space and transfer objects to this dimension."
"How can I achieve Mangekyou Sharingan like you?" Raven could do whatever it took to get those eyes. After all, her mind was corrupted by the thirst for power like all Uchihas and the idea of possessing Mangekyou Sharingan just made it worse.
"..." Obito fell silent and hesitated a bit. He was not sure whether to say it to her or not. In the end, whatever was destined to happen would eventually occur. He knew her Mangekyou Sharingan's awakening would be inevitable in the future. Thus, the masked Uchiha finally told her the formula to get them.
"Kill those who you cherish most."
The Roost, Nagozara City
Within the abandoned city since the 3rd Honkai eruption in 2014, there was a shabby shelter called the Roost. It was made by Raven as a home for orphans surviving the Honkai Eruption. Unlike other citizens who were killed by Honkai illness, these children were born with high Honkai resistance which saved their life. Despite living in an environment contaminated with Honkai radiation, the orphans were still growing healthily.
Raven - their caretaker brought in supplies and food every now and then to the Roost. The orphans saw her as their second mother, who was compassionate and good-hearted. However, today would be the end of that happy story.
"You're back, Sensei! Everyone, Sensei has returned!" As usual, Sora immediately notified her fellows when Raven arrived with a white-masked stranger. He whispered something in Raven's ears before jumping to a roof nearby to observe.
"I won't interfere... it's up to you now."
The children soon gathered around Raven in happiness. But that atmosphere did not last long. Sora noticed something wrong with her caretaker. Contrary to their mood, she showed a melancholy expression and didn't say a word. After a while, Raven finally opened her mouth and spoke something.
"Chidori!" Raven's sharp claws glowed as she imbued them with Lighting Release. A few minutes ago, Ghost had shown her a technique named Chidori and let her copy it with the Sharingan. The technique itself was not difficult to perform since it just require 3 hand signs.
"Forgive me." Raven stated sorrowfully while tears ran down her face. The first victim she chose was Lyle. The ill-fated boy could not even react when Raven used her lightning claws to tear up his little body. After Lyle was killed, a tomoe appeared on her Sharingan, increasing the total number to 2.
Other orphans were stunned by shock. They witnessed their caretaker kill a friend right in front of them without any mercy. They were swallowed up by fear to the point of not being able to move even an inch. As a consequence, they also joined with Lyle and received their brutal deaths from Raven's lightning fang. The only one left now was Sora.
"Sensei, do you know what you did?" Sora yelled in madness but it could not stop her trembling. She awaited the answer but never got it. In the end, she raised her head to look at Raven's eyes, which caught her frightened. They were no longer the warm crimson eyes she was familiar with. They had changed to have the pattern of a three-pronged shuriken.
"I'm aware of my deed, Sora. Now answer my question. would you like to have a peaceful death?" Raven asked her in a cold voice.
"Tsukyomi!" Sora's vision suddenly went black as she lost consciousness. The little girl fell but was caught by Raven in time. The sound of slow footsteps resounded and Ghost appeared right in front of her within seconds.
"Congratulation! You've achieved Mangekyou Sharingan as you wished. Now do mind telling me what've you done to this girl?"
"I cast Tsukyomi on her. She's having a happy life in the Genjutsu world. It's a place where Honkai doesn't exist and her parents were still alive. But when that dream ends, she will die in real life." Obito was silent after hearing that. Coincidentally, Itachi had killed his girlfriend the same way as Raven did. No one knew what exactly Obito was thinking at the moment but he then had a mysterious smile.
"Excellent! It's just as Madara and I expected. Everything is going exactly as planned."