The second part is not possible because the Will of the plane is not willing to speak with him much less exchange helpful information with him.
So what he has to do to get the information he needs is clear. He just has to gut the Will of the plane and examine its entrails. It is a figure of speech but what he intends to do is not far from it.
He said in anticipation, "I will hold it down, open it up, and look inside of it. We will see how it can remain snubby then."
The next thing he did was to cut out pieces of his soul. These pieces are connected to him through a thread thanks to his spark of consciousness. But they are without memories and soul imprints.
It was very easy to do. It wasn't painful at all because he has mastered control over the spiritual matter that makes up the soul. The only advantage is that it weakened his soul. But that wasn't a problem for him since he can now devour other souls without issues.
He used these pure soul fragments to infect everyone. Even transcendents were infected. They could resist the previous infection somewhat but their existence didn't notice this infection at all.
Those who were infected had their memories and soul imprints changed to his. So they became his clones. In this way, he became connected to the Will of the plane without being born in the plane. He doesn't need to possess the child of the plane directly anymore to gain access to the Will of the plane.
This way his infection spread rapidly through the plane which created enough spiritual influence for him to make contact with the Will of the plane and attack it.
He chuckled evilly, "You think you can look down on me? Then you have another thing coming."
If he had hands, he would be rubbing them against each other right now. It is needless to say he is going to enjoy himself immensely with what he is about to do.
Only the gods were exempted because they were still aware of the infection. Their divine will and divinity make them aware of changes to their soul and very resistant to his infection.
Plus the soul fragments had to pass through their god fire to reach their divine soul. They were burned up so the gods were not infected. As for the others, they didn't even know that they were infected.
So the battle between the two spiritual entities in the plane started. It is unlike any spiritual battle that he has engaged in. It is more of a tug of war than an exchange of blows.
The battlefield is every living thing he has infected. Legion-7 was eroding the Will of the plane through them to weaken it. This is easy for him to do thanks to his soul fire and soul force.
The Will of the plane on the other hand can only resist. It can't retaliate in any direct manner. It is not alone in this fight though. Every inhabitant of the plane can help it to kill Legion-7. The most threatening of them is the child of the plane.
But Legion-7 wanted the child of the plane to appear and confront him. That way, he would be able to end the fight early. After all, a direct channel to the core of the Will of the plane is much better than using peripheral connections to attack the Will of the plane.
So Legion-7 advised sincerely, "Bring out the child of the plane. Bring out your champion. You don't have any other choice. Who else is going to save you from me?"
The Will of the plane didn't listen or speak to him. It made him scoff. "Keep being stubborn. Let me see who will save you from me."
Apart from the gods, there are no other strong entities in the plane. There are no titans of law in the plane at all because of the lack of origin energy. The strongest beings in the plane on the path of perfection are transcendents. They can't even become lords of law since they can't leave the plane.
The gods have sealed the planar portal and the sky. They did it to maintain their control of the plane. This decision has doomed them now. There is no one strong enough to inform them that the "disease" has evolved and has become much more sinister.
Despite the unfavorable situation, the Will of the plane refused to give up. As the embodiment of the will to live of all the living things in the plane, it will keep struggling for a chance of survival. So It pushed him back and prevented him from making any progress. But its resistance was waning rapidly as the infection spread to more living things.
Legion-7 smiled and said, "Let us see how far you will go with your struggles."
He has infinite Origin energy so creating soul fragments and converting them into soul essence by eating them makes it so that he can spread himself out in the form of clones and attack the will of the plane from many directions.
The Will of the plane is stronger than him now so it can resist easily. But that will change as the number of living things in the plane die. His attacks will also become lethal to the will of the plane the greater the percentage of the living things in the plane are under his control. So by the looks of things, he is going to win this tug of war.
He said proudly, "I am not a demon god, but I am good enough to take you down."
He attacked the will of the plane on a spiritual level while also using his zombies to kill the living things in the plane. It is a double-pronged attack on the spiritual and physical level. It is exactly what a demon god would do to defeat the Will of the plane.