Which s why he had to go to the military (school)

When he was turned to stone for two years

Here's the concept.

A long time before the novel even starts Human eradicated monsters in a big war, why? Fantasy racism, the reason the novel gives is that due to prejudice people didn't believe that these monsters had sentience and all of them were evil. The people who lead this literal witch hunt were the impirial family which is how they came into power and stayed so for atleast a thousand years.

The Impirial Family are introduced as bad guys, not only because all the power they have is from a genoiced but also because they betrayed the MC in the first chapter.

So far so (actually) good.

The monsters that went into hiding in order to escape total annihilation come back and want revenge, in order to do that they made a deal with dark gods, often betraying the good or doing other morally bad things in order to gain the power to whoop ass. It gives them a sense of moral grayness. Their motivation are entirely justified, no questions asked. They way they go on to do their revenge? No so much.

In contrast to that is the MC who also got betrayed by the Impirial family has vocalized his hatred towards them throughout the story quite a bit. His solution is to make the north independent and take the power from the center (impirial power) throughout this war and probably charge them guilty for most of the crimes they have committed.

A long story short he wants revenge without sacrificing his moral in comparision to the monsters.

Making this war quite morally interesting.

The problem I have is that the battlefield introduced until now are all the same

Northeast battle:
-Monster (humanoid) corrupt/take hostage a dive being/thing
-They open a portal for less sentient but op Monsters from the side of the evil gods they are in contract with to come in.
-This is bad because it can literally ruin the Land itself (think fantasy nuke)
-Iron stops this, makes contract/gets help from with said devine being.

Eastern battle:
-Monster (humanoid) corrupt/take hostage a dive being/thing
-They open a portal for less sentient but op Monsters from the side of the evil gods they are in contract with to come in.
-This is bad because it can literally ruin the Land itself (think fantasy nuke)
-Iron stops this, makes contract/gets help from with said devine being.

North battle (until now) :
-Monster (humanoid) corrupt/take hostage a dive being/thing
-They open a portal for less sentient but op Monsters from the side of the evil gods they are in contract with to come in.
-This is bad because it can literally ruin the Land itself (think fantasy nuke)

Of course there are some differences, some even quite important but overarchingly this is how it goes everytime. Pair this with the problem of the power system being used more as a mild suggestion for the MC rather than an actual limitation on who he can fight and win against and who not and every monster being either master (highest) level or being described as "similiar" "close" "or theoretically speaken" to that level.

the monsters are describes as this ultra force that needs to be reckoned with and you can't casually f*ck with and humans are described as being in a situation where they die off too quick making the forces that are actually capable of killing them way too rare to actually make a dent. Meaning more soldats are dying than are being recruited. At this point in the novel humans schould have died out already because this war is not sustainable.

So either the Author suddenly pulls out something that fixes that or this sort of suspension of disbelief is going to ruin what is actually a quite interesting take on "war" in novel.