The Extreme Basic Understanding Rank was the same as Void Marrow, and while Cain had to go through countless ordeals and nearly lost his life to achieve it, the Scarlet King only had to remain in cultivation for less than three months.
The Scarlet King felt how the meridians had already spread over every corner of his body, even reaching his brain, and knew it was time to advance further. While the Wave Warrior Rank was nearly identical to the Essence Evolution Path of Power and the Astral Rebirth Path of Power, there was a complete change in paradigm from the Wave Champion Rank and beyond.
While a Wave Champion of the Astral Rebirth Path of Power would reforge their bones, someone of the Essence Evolution Path of Power would focus on their Evolution Core, generating a qualitative change in their energy pool.