After one week of travel, I arrived with my Army Group in the Eastern Region of the Mainland of Yestera Plane. After arriving in the Eastern Region, I immediately unleashed my Mechanical Legion, which started annihilating one tribe after another.

I have even killed several General Level monsters, mainly those that could be used for Devour ability, while the rest of those, who weren't suitable, were blasted to meat paste by main cannons of Lunar-Class Cruisers.

After another weak, the entire Eastern Region was almost wholly cleaned from any signs of life. All monsters, goblinoids, orcs, trolls, giants, and other species were killed.

One week later, the entire Eastern Region was entirely under my control when the last General Level monsters were slain by me yesterday. I got reports from General Zagan and Venelana that they were too done with their part.

Only General Zagan had some problems, as he was forced to fight sea monsters that attacked the shores of the Northern Region, and countless merfolk attacked the mainland under the leadership of three Pinnacle General Level merfolk.

Thanks to his ten Ultimate-Class Flesh Golems and help from General Amyke, they were able to kill them all and push merfolk back to the sea. He also started constructing the fortified lines through the shores due to fear of merfolk invasion happening again, which was realistic suspicion.

They too were returning to meet with; only General Zagan left the majority of his Army Group in the Northern Region until the fortified line on the shores of the Northern Region was constructed.

It was understandable that those sea monsters would try to conquer the mainland when they sensed the death of countless General Level monsters. Fortunately, only weaker ones came, and they didn't wake up and bring those Monarch Level entities from the depths of seas and oceans.

In the future, when I reach Satan-Class and have several Satan-Class subordinates under me and more advanced arcanotech, I will hunt every one of them. The bottom of the sea was probably the most precious bank of resources.

From Devouring all those General Level monsters, what was a good thing, my Demonic Energy reserves have risen to 240 Units. Thanks to my mastery over Tier Magic System and Dark Light Trait, I had terrifying combat prowess among the Ultimate-Class powerhouses; the only thing that was limiting me was my energy reserves.

Before the Great War started, I wanted to reach Satan-Class.

Rizevim was already one for a long time, and as a Satan-Class entity, I would have probably the best chances to survive the Great War without being killed or crippled. On top of that, It would give me freedom during the war and an opportunity to increase my social standing and prestige.

After the Great War ends, it would be the best chance to execute a coup d'etat and rule the Underworld.

I left my adjutant in charge of clean-up works, and construction works in the Eastern Region were left to Architect's overseeing as I took one Cruiser and left for the meeting with Venelana and General Zagan to conclude this entire thing and finally return home.

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After more than ten hours of traveling in the Cruiser, I finally arrived at the meeting point, where General Zagan was already waiting for me.

"My Lord."

He bowed slightly as he greeted me.

"General."

I said to him.

"Good job with the merfolk, I must say... I didn't think they would attack this soon."

I praised him sincerely. As my best subordinate, who served my family for centuries, he did splendid work with invasion attempts from the side of merfolk.

"Thank you for your praise, My Lord."

He said to me.

"When the plane is industrialized, I will reward your family with one Mechanical Legion and five Lunar-Class Cruisers and a battalion of Anti-Matter Magicule Canon Batteries."

I said.

I deemed this as an appropriate reward for his service and merit achieved during the planar conquest.

"I am honored, My Lord."

He bowed slightly, expressing his gratitude.

"And now even Venelana is here."

I said as I saw another Lunar-Class Cruiser coming. This Plane was still developing, and due to certain factors, it wasn't the best decision to travel through teleportation spells in the Yestera, at least yet. Even me building a teleportation formation to transport troops from Ewor to Ihor was a great risk.

"Now, where is Lord Mephisto Pheles?"

I ask as we gather here.

"My Lord, Lord Pheles has decided to stay here and study the development of the Laws of the World. Currently, this Plane is undergoing evolution to reach the Grade 7 Plane. He suspects that there may be a reason why there were already several Monarch Level monsters in this Plane, even though this Plane is right now Grade 8 and shouldn't possibly hold them so well..."

General Zagan attempted to explain to me, but his knowledge about this topic was low, so it sounded pretty terrible, but I was aware of why Mephisto would stay here.

Typically for planes to evolve into higher grades, there are two possibilities. One is natural by aging. This path could take hundreds of thousands of years at the shortest, and millions usually. The second path was letting the Plane devour other planes. Or rather, it was done by extraction of the World's Core and letting another World's Core absorb its energy.

From what I read about Astral Boundary Universe, the second most common reason behind planar conquest was precisely this. Strong factions would often wage wars to obtain more World Cores to fasten the evolution of their own Plane. That would bring them many benefits, such as more God Slots, higher energy density, size expansion, and many others.

A long time ago, there were even wars between Universes, but I didn't have many records about that.

"Then let him stay. Additionally, General Amyke will stay here permanently, together with all Mech Drones, all Voidships, and Mechanical Legions. Half of the Devil Soldiers we brought here would be stationed here to protect the Plane until the complete defense system is done and fortifications are constructed."