Power Levels (According to Ryuu):

Warning! This is purely for the curious ones. There's no need to see this, as I will introduce some of them properly as the story progresses. At the end of this auxiliary chapter, I've also dropped a huge spoiler and a little Trivia.

[ENTRY LEVEL] : Just formed their Mana Core. Their strength is around the strongest fighters on earth.

[NOVICE] : From this stage, any being from the 'Outer' can start using Mana, though they barely started on the arduous path of power, which makes them extremely weak as they have no real method to use it.

[INTERMEDIATE] : At this rank, beings from the 'Outer' are able to imbue Mana into physical objects for a short period of time. This allows them to easily defeat weaker opponents by enhancing their weapons. In comparison, individuals at lower ranks are unable to imbue Mana into objects in this way.

[ADEPT]: This rank separates the weak from the strong. At this stage, individuals are able to hold their Mana inside an object for a longer period of time than those at lower ranks. However, the true defining characteristic of this rank is the ability to imbue their own body with mana.

[OVERLORD] : This rank marks the beginning of a greater journey on the path of power. At this stage, individuals are able to imbue Mana into the atmosphere and solidify it. They have also mastered the use of strengthening their bodies. It's important to note that imbuing Mana into their body is only temporary, as there is normally no way to truly store it inside the body without causing it to collapse, unlike Ryuu who for special reasons was forced to do so.

[KING] : This stage is what most seniors in the Dragon Race were at. At the [OVERLORD] rank, perfect control of mana has already been achieved. What is required to reach this stage is to use the perfectly controlled mana to slowly refine the Mana Core endlessly. In time, their authority over mana will grow over and over. Once this stage is accomplished, forming a [Domain] becomes possible.

[EMPEROR] : ???

[???] : This rank is a particular stage that even Ryuu has not heard the name of. Few beings in the entirety of the 'Outer' have reached this stage, as their level of power is stronger than even the Oldest Gods such as Ouranos.

(Little Trivia: Before Chapter 1, Ryuu was at the boundary of the [OVERLORD] rank and almost had refined completely his [Mana Core].)

(Huge Spoiler: The world couldn't accept the difference in realms, hence the reason Ryuu couldn't keep his [OVERLORD] rank properly. This may even explain something about the "truth" of this whole thing. It's up to y'all to get, though.)