Unbelievable

Rai was still thinking about how he almost died as he was touring the hall . He came across a huge pattern laid on the floor with weird designs around it . He was curious about it when heard Akasa say "That's the mana gathering formation set up for you , it helps in the faster convergence of mana . So with more mana available , you would be progressing faster in your cultivation . " Rai was still unsure and asked "Are formations something like artifacts or something ?" . Akasa hearing this said "they are totally different . Formations are like engravings with special properties which altogether perform a specific function . Formation specialists are highly sought after in many clans and our master was also good at formations as he was able to construct universe level formations with a little help though.(same levels as artifacts)

Akasa quickly accessed the castle's library looking for a cultivation manual suitable for Rai . There were thousands of manuals and all very relatively high level as they were a collection of master Akihiko. He eventually found three which were very suitable for Rai which were named Astral Mana scripture , Chaos devouring mana scripture and finally the Solaris scripture . Each manual had its own advantage . The Astral Mana scripture made it so that the person cultivating the scripture had immense mana capacity as huge as stars and Solaris scripture changed nature of the mana into fire ( The purest fire to ever exist , The Solaris flame) and finally the chaos devouring mana scripture was a bit of a cheat code as it could allow the cultivator to devour any energy into purest mana and observe it but it needed a cosmos level physique as it was able to adapt to any form of mana which was perfect for Akihiko.

Akasa gave Rai three manuals and explained the advantages of each one . Rai was immediately drawn to the chaos devouring mana scripture as he imagined himself devouring all his enemies to his own cultivation and thought that his journey was more likely that of a villain rather than a hero .Rai chose the manual and Akasa transferred the knowledge of the body tempering realm which was filled with ten levels and Rai had to temper specific parts of his body to perfection in different levels . Rai was surprised that Akasa had this sort of function but he remembered that he never explored its functions which was kind of embarrassing . 

Akasa instructed Rai to sit in the centre of the formation and start cultivating according to the manual . Rai immediately sat down and began cultivating . He first felt the mana around him as he had already used his will to draw it around him when executing the move which almost killed him . The mana was already very dense and was steadily increasing when Akasa started the formation. He started to pull the mana into his meridians which were already opened according to the manual .The mana was being devoured and being converted into purest mana which permeated through all his body and expelled all the impurities accumulated in his body . Rai didn't mind the foul smell of the impurities as he was deeply obsessed with the feeling of the rising power of his body. He was completing cycles of this process within seconds as his body was reaching the levels of perfection . 

As soon as he felt that there were no more impurities in his body , he continued and entered the level 1 of body tempering realm where he tempered the skin all over his body. It was incredibly painful was the pure mana was just continuously destroying his skin and repairing it immediately. Usually cultivators would just cultivate one cycle of destruction and repair and rest for a while and continued but Rai was just taking all the pain as if it was nothing . Akasa was just dumbfounded and thought that Rai would take break after an hour of such mind numbing pain but was completely wrong as Rai just kept on going . Even after reaching sufficient standards of tempering , Rai was not satisfied . He thought why be average when you could be great and strived for the extreme perfection . Rai eventually felt no more room for tempering the skin and entered level 2.

Akasa was proud on seeing Rai so motivated which resembled their master Akihiko but one thing it felt unbelievable about was the speed at Rai was crossing the levels of body tempering . Within four hours , Rai already reached level 7 and was tempering his organs . This was record breaking and it attributed this feat to his master's unfound levels of pain resistance . Rai on the other hand felt it was incredibly slow but didn't know that what he was doing would be seen as inhuman and monstrous in the cosmos.