Cultivation manuals in the whole Three Heavens are divided into 9 Ranks, with Rank 1 being the lowest while the Rank 9 is the highest and most treasured.
However, in the Lower Heavens, cultivation manuals that were known to exist were only from Rank 1 to Rank 5.
There were only three known Rank 5 cultivation manuals, excluding the Unranked ones like the Gracious Sword Technique.
This technique was termed unranked because no one could properly judge its Rank. It could help the cultivators in comprehending Sword Intent, which should have placed it in above Rank 5 category however, except for Yuan Xuming, no one ever succeeded but instead they suffered Qi Deviation, so this manual should be placed in Rank 1 rather than above Rank 5. In the end, it's rank was not decided, and it became Unranked Cultivation Manual.
As for Rank 4 cultivation manuals, they were always a rarity even in top powerful sects and organizations of Lower Heavens.
Few decades earlier when there was too much chaos because of low availability of Rank 4 cultivation manuals, what these organisations did was that they created copies of these manuals. The copies were then shared between friendly sects. This slowly led to most of the Rank 4 cultivation manuals becoming common manuals, present in almost every sect.
One would think that after all the sects have acquired a Rank 4 cultivation manual, it should have lost its charm. However, what actually happened was opposite. In fact, some cases were a bit terrifying.
In one case, a sect did share the cultivation manual, but they altered it a bit. This decreased the manual efficiency and affected it's subsequent copies, eventually ending with a copy which did more harm to the cultivator than increasing their power.
In another extreme case, a sect which got a cultivation manual from a friendly sect lost one of their talented Disciple due to flaws in the copied cultivation manuals.
Such cases led to infighting and chaos among these friendly sect alliances, eventually most of them broke and ended up becoming mortal enemies rather than benefactors of each other.
The plan which was supposed to help and grow everyone ended up creating more trouble. No one knew who came up with this plan or what their real intentions were, but many secretly pointed their fingers towards the Crimson Pavilion, which is the most powerful organisation of the Lower Heavens.
Without Crimson Pavilion's agreement, this wouldn't have been possible, and many powers wouldn't have agreed to share their Rank 4 cultivation manuals.
However, even if people did blame the Crimson Pavilion secretly, no one dared to say it loud. Neither the other top sects, nor peak cultivators of the Lower Heavens.
What they did do was slowly remove copied Rank 4 cultivation manuals from their own sects and used only verified and genuine cultivation manuals.
This also led to more issues, like without trying a cultivation manual, no one knew if it had flaws or not. They didn't know if the cultivation manual in front of them was a treasure or a death trap.
With no ways to decide, the people were forced to use guinea pigs. These guinea pigs were none other than the weak cultivators from weak sects and clans.
If these weak cultivators succeeded, which was a rarity in itself, the sects would then take them in as Elders or give them certain benefits.
But if they failed and ended up crippling themselves, the sects will not do anything. In fact, they would wipe out all the traces of this incident by literally killing off the weak cultivators and their families.
This thing was prevalent for many years before it slowly became a distant past, However, to Ye Tian Yun, all this was very important. He knew all this. He even knew who the main perpetrator was, in fact, he even knew why they did it. No, they were not the Crimson Pavilion. In fact, the cultivators of the Lower Heavens had only one role in this scheme, and that was of being the victim.. This included the most powerful organisation, the Crimson Pavilion.