This is a ctrl+c/ctrl+v from what i commented on MD with a few edits. The review is further down.
Interesting manga with a shit ending. 6.5/10 (honestly maybe a 6 is already too much, but i enjoyed it besides the final chapter)
The story wasn't developed enough, they rushed everything after a certain part (more than it already was lol) and the character.. Well, he was an interesting character but wasn't developed enough as well. All i can see is a bunch of potential going to waste here.
Maybe this can be described as a shorter, worse version, of "Arifureta Shokugyou de Sekai Saikyou" ? Both have the same problems but arifureta is a little more developed, has a better character and a more interesting story (imo), this is judging by the current manga ch. btw, i didn't read the novel.
Anyway, Dungeon Seeker ended like a shit movie that was not supposed to get a sequel, i'm quite disappointed.
---Now to the actual review---
You can read the synopsis, so i'll skip that. The manga goes from 0 to a 100 in a matter of a few chapters, and then it falls under a boring part, returns to a interesting part of the story to end with a completely shit conclusion. If you want a quick read, go for it, otherwise don't bother. What you can actually expect from it is the regular isekai thing, with a darker world and a mc that is ok with killing people. Like i said, you can compare it with Arifureta.
Personally i read this thing within a few days while i was in the bus lol