Revelation
It took Karasu's group a week to reach the underground temple that Karasu had spotted, giving them time to continue honing their abilities. Shiro's prediction of Karasu quickly mastering the Ryugan proved true. By the time they reached the cave entrance to the temple, Karasu was able to keep the Ryugan active for the better part of a day without it tiring him out. He had continued to keep an eye on the temple as they traveled, using the hidden structure as the focal point of training his new ocular abilities. He had come to learn that Ryugan combined the abilities of his Kokuryutei Sharingan and Shiro's Byakugan, allowing him to cast even the Tsukuyomi on multiple targets without them having to look into his eyes.
Inu had taken the time of their journey to try teaching Karasu and Usagi his clan's purer version of the man-beast transformation, a transformation that would give them a form more like the beasts within them. Usagi had been unable to learn the technique, due to the violent and malicious nature of the Nine-tails fragment. Karasu had no such difficulty, taking on a new dragon form that didn't require the use of dragon fire. His transformation caused his pale white skin to become ash grey as it became as hard as the dragons' scales, allowing him to withstand powerful attacks while taking little to no damage, even Inu in his transformed state couldn't do anything to penetrate Karasu's hide in his new form. One thing that none of them understood at the time were the bones that would emerge to form a mask, wings and a tail. The wings were devoid of any flesh, covered instead by Koku's black fire.
Karasu used the technique Inu had taught him as they neared the cave, going so far as to activate his Ryugan in tandem. The result was a more intense transformation, his skin actually becoming dragon scales instead of merely hardening like them. He cast his sight into the warren of caves leading to the temple below, ensnaring every enemy with the Tsukuyomi or consuming them with dragon fire from a distance. It allowed them to reach Kaguya's temple much easier and faster, with whatever enemies that were still alive being paralyzed within their own minds.
Karasu stopped as they reached the temple's entrance, returning to his regular form, though he did keep his Ryugan activated as a precaution. He placed his hand upon the slab with a carving of the Rinnesharingan, gasping in surprise as the image shifted into a depiction of his Ryugan. A dull boom sounded from within the temple itself as the image finished forming.
"Do you think that was a trap of some sort?" Inu asked quietly. Karasu shook his head.
"I think it was a door that only the Ryugan can open," he replied, searching the temple with the aforementioned Dojutsu.
His Ryugan could not penetrate the doorway from outside, nor could Inu or Usagi see anything within the gloom. All that changed the moment they crossed the threshold. Near the back of the room was a raised platform of stone, three large skeletons upon it. Karasu recognized their shape as he got closer, realizing that he was looking at dragon bones.
"I had forgotten this place," Koku said sadly through a wisp, to which Shiro replied that neither did he as he too spawned a wisp.
"What is this place?" Karasu asked the dragons.
"This is where our bodies were placed after our souls were extracted by Kaguya. She had hoped to feed our life force to the tree that would create the Chakra fruit to make it more powerful. Her plan backfired, for she did not know that she was pregnant when she took our souls into her body. She unknowingly gave us new hosts, which is how our power came to be a part of her Otsutsuki lineage," Koku explained aloud, for the benefit of the others.
"You must remember, we are living weapons created by the Otsutsuki clan, but our power had ever been our own before we bonded with the pair of embryos in her womb. It was through this mix that the Byakugan, Sharingan, and even the Rinnegan came to be. Kaguya's clan may have had ocular abilities of their own, but we were the ultimate form of the Otsutsuki's own power," Shiro added.
"Wait, I count three skulls here," Inu said.
"Yes, Aka. He was ever an angry one; he too, had his soul taken. But it was one of Kaguya's son's, the one who I had bonded with. It was the combination of our power that created the Rinnegan," Koku said.
"Why have I never felt his presence?" Karasu asked the black dragon.
"I do not know," he replied.
"Karasu, look at this!" Usagi suddenly called from the back of the room.
Karasu made his way around the dragons' bodies to where she was, being careful not to disturb the bones. His eyes went wide as he beheld what she had wanted him to see; the back wall was completely covered in strange runes and symbols. Karasu's Ryugan was able to make sense of the marks in the stone, revealing it to be a chronicle of the events starting with the dragons' arrival to Earth and ending with Kaguya removing their souls, along with a warning from Kaguya's children. It detailed their experiences with the dragons they played host to, the same ones that now lived in Karasu. As far as he could tell, he had already learned most of what they wrote for himself. One thing he hadn't experienced in all his time using the dragons' power that did affect Kaguya's offspring was almost always being incapacitated after using the dragons' powers, apparently it had caused them a great deal of pain whenever they used them.
"Can you read it?" Usagi asked Karasu quietly.
He nodded, reading the text aloud so that she and Inu could be kept in the loop. They were both left stunned as he concluded his translation, at the fear that the brothers had expressed of the dragons being released into the world again when they died. They hadn't known that the dragons would go dormant and continue through their bloodlines, only awakening when the blood of their host was closer to the Original Otsutsuki line. Karasu felt a strange sense of anticipation and longing as he looked at the Otsutsuki's emblem.
"There's another door over here!" Inu called from near the back corner of the chamber.
Karasu and Usagi joined him, readying themselves as he pushed the wooden door open. Behind it was a small room loned with shelves of scrolls, a few chests scattered about the corners. There was a tall object centered against the back wall covered in a black cloth, something at its base giving it a strange shape. Usagi and Inu immediately began searching the scrolls and chests, finding a horde of knowledge and history thought to be lost to time long ago. Karasu's attention was solely on the object in the back, feeling as though it were calling to him. He walked up and pulled the cloth aside, leting out a gasp as its secret was revealed. The cloth had been covering a stand with a stylized mask reminiscent of the Anbu, though it was contoured like a dragon's head. Resting against the stand was a long, narrow box tied with a piece of red ribbon. Karasu took the box and opened it, finding a small sword in a beautifully decorated sheath. He pulled the sword part of the way out, surprised to see that it wasn't metal; it looked more like bone. As he pulled it completely free of the sheath, the blade became covered in ethereal red flames.
"Those are Aka's flames," Shiro exclaimed in surprise.
"It must have been made with one of his claws or fangs," Koku added, his voice sad. Karasu shared his sentiment, not liking the idea of someone desecrating the dragons' corpses.
"If this is a part of Aka, then I'd say it now belongs to me," Karasu said, returning the dragon sword back to its sheath reverantly.
Karasu also took the mask, almost missing the small chest on the floor by his feet. He opened it carefully, shocked by what he found. Nestled within the chest was a cloak that looked like it was made from Aka's hide, covered in ruby-red scales that shimmered in the light. He put on the equipment he had found, feeling like he had found a piece of himself that he hadn't realized was missing. It was comforting. Inu let out a low whistle when he noticed Karasu's new look.
"Now something about that just seems right," he said.
"We should get going when you two are finished. There are bound to be more places like this scattered about the various Lands," Karasu said.
"There's also the matter of making sure Danzo's Foundation is completely dismantled," he added, his voice seething with hatred.