To clarify, this novel's cultivation begins at -
1. Foundation Realm (Not given much attention actually. MC passed it in few chapters)
2. Gathering Qi Realm (Just as the name suggests, starts to gather Qi in body and could use martial arts that utlizes the Qi)
3. Bone Forging Realm (Just as the name suggests, using Qi to nourish the bones. Cultivators at this realm has higher defensive capabilities)
4. Tian Xuan Realm (A leap in battle strength compared to the previous one - higher offensive and defensive capabilities ).
5. Shen Zhao Realm translated as Soul Illumination Realm here (Could utilize divine sense or simply just mental strength to attack)
Each rank has 9 levels. After the ninth level, it will be elevated to next rank. Until then, it is a bottleneck.
Of course, there are higher ranks but these will be slowly unraveled in the manhua later on. For example, emperor level like the MC (previously) and also a saint level that caused the MC to die in his previous life. Yes, MC is forced to commit suicide by the saint level expert and not being backstabbed by his student in the original novel. All his student did in the novel is just notify the other six emperor level experts that his teacher has gotten the relics of the one of the ancient powerhouse.
Hope this would be able to help a little seeing that this manhua had been garnering some attention as of late.