The way the believers view a god determines what is compatible with the god. Zernon is seen as a strict god with rules and regulations. He likes law and meting out justice. He protects the mortals by keeping order in the mortal realm. He is the god of order and justice. His believers don't see him as a sunny god that brings life and light. He doesn't invoke happiness in them as the sun god does. He is more like a strict father that is always frowning at misdeeds and punishing rule breakers so the domain of the sun is not compatible with his divine image.
The god of the sun on the other hand is ancient. He is very powerful and very wise. He brings light and life. He and the domain of order is not a perfect match but they can see him using his incredible power to maintain order in the plane. So the domain of order is compatible with him. He is fusing with it and will then become a level two Celestial.
Then he will need a domain that is compatible with both the sun and the order for him to become a level three Celestial. The god of fate is very compatible with Order but he didn't take it because of karma. He made sure that there is no leverage of karma between him and Legion by giving all of them what they deserve.
He gave nothing more or less than what they deserved so that they will not be able to have any hold on him. He doesn't need the domain anyway. The Authority of the Celestial Supreme makes him a level-two Celestial without needing to upgrade himself. That is enough for him to be untouchable in the divine plane.
There is more to power and survivability apart from the level of Authority. Zernon was a level three Celestial as the Celestial Supreme but he couldn't kill the level one god of fate. His power didn't stop him from being killed at the end of the day.
Domain interaction is very important when gods fight for supremacy. Stelios won't be able to match Zerkon now that he is a level-two Celestial. Not that he needs to worry about that kind of thing. It is a fight that cannot happen anymore. Fighting amongst gods is not in Stelios's future anymore. He has a very important job for the upcoming experiment. That should make him very busy for the nearest foreseeable future.
The orange orb within Helios's Stigmata finally finished evolving. It glowed brightly and became completely white. Helios began to glow too as Stelios finished his evolution. Stelios woke up to an unfamiliar and yet familiar void. It took a while for him to figure out where he is. He has been shackled by crystal vines that have wormed their way into his body. The vines are siphoning his divine power for Helios to use. Stelios started to panic after realizing his situation. Then he began to beg.
"Please. Please. I beg of you. I will do anything you want if you will let me go. Please."
Helios ignored his pleas. He said to all of Legion, "I have everything now. We can move on to the next phase."
The sun domain contains elements of both light and fire. It has elements of order now Stelios has absorbed the domain of order. Helios has fragments of the law of fire, light, and order in his body. Those fragments have finally been complimented with similar divine power. It has elevated his body from that of a half-celestial into a temporary body of divine law as long as Stelios stays within the divine engine.
This is necessary for their next experiment. He theorized that the rune-creation ability of giants might lead to the answer about Authority. Runes are actually fragments of the law of Order made to create things using divine power.
Authority is the foundation of power in the void universe. It is also the source of power for gods. It is bestowed to them by the plane through their domains. It produces the divine power that is used to subvert laws, including the law of order itself.
Divine power subverts all types of laws. Gods use it to impose their will upon the world instead of comprehending laws. But it is only the subversion of order that leads to limited creation. So the authority of gods is a very important item to study if Legion intends to crack Authority or at least get to the bottom of creation without being a world god.
The importance of Authority cannot be understated. Gods need it and so do those on the path of perfection. Even do need Authority. They all have different sources but they grant power.
Those on the path of perfection get theirs through comprehending laws and the subsequent bestowal of it by the universe as a reward for their effort. Demons are granted one when they pass the trial of the abyss, then they have to get more by killing Celestials. Gods get theirs when they are elevated by faith and receive the plane's acknowledgment.
In every case, Authority is granted from an external source. Legion hopes to crack the secret of its creation and become able to bestow it upon itself or at least change it. Every clone of Legion has put a lot of effort into this endeavor. They have fully analyzed the Authority of gods and the Authority of sovereigns. But they haven't analyzed the Authority of Chaos. It is what they hope to achieve today.
They hoped to acquire information about the Authority of demons but they don't have the authority of other demon kings to work so they will have to work with Aeternus's Authority over Chaos even though it is dangerous. Chaos is dangerous since it tries to destroy everything that it comes in contact with.
Demons are associated with Chaos so the information that they get from Aeternus should be relevant, unbiased, and primal, unlike the several types of Authority of demons. The alternative is to acquire several types of Authority from the different sins but that is tedious and unreliable.