Hello, believe me, I was very surprised to find a fanfic about the birth of the demonic sword and just the type I was looking for, which is from the term reincarnated. I apologize in advance if the English is not that good, I am using a translator to send you this comment. Anyway, I've seen a couple of chapters of your fanfic and I'll leave you a brief review of what I think about it. First of all, the character/mc is interesting, he is not the type I like, but he is still interesting, a nobleman with little talent who was later replaced by the reincarnated MC, the introduction seems good to me, but I think you could have given more details on how this one died (unless I ate most of it and didn't read it).
However, complications begin when you introduce the MC traveling to other worlds. The beginning with Elden Ring is good, calm, slow, the MC gathering information, we're going well so far.
The problem comes when at one point in the story everything goes absolutely fast. You literally introduce a lot of Elden Ring events so lightly that it is not understood very well, at least that was my case, I don't know if the same would happen to other readers like me. In addition, there may be certain complications for people who have not played the game (Elden Ring) and do not know what its story is about, like me for example, it gave me a big headache to see so many names, characters and things that I did not know , I had to go on the Internet to more or less know what they were, which greatly reduced the quality of my reading.
I personally don't like the harem, but it's your story and I respect that you want to implement it.
But there are also quite interesting concepts, such as the individuality of the MC, who, according to what I read, is capable of copying elements, something very peculiar that could not have occurred to me.
However, there are also negative things, the speed with which things are done at the beginning is one of them, along with the introduction of concepts that are not understood very well about Elden Ring, it even gave me a headache and even I skipped chapters 7, 8, 9, 10, because I got tired of not understanding much of the events you were trying to convey to me.
From chapter 11 there is a big time jump, which is fine, and there is not much more to comment on my part, except that from that moment on I felt that the protagonist gained a lot of power (I think it is partly my fault for having skipped chapters 7, 8, 9 and 10 in which I believe other topics related to MC's personal power were discussed, such as his transformation into a hybrid dragon)
In short, the idea is good, a very interesting concept of a fanfic that I was looking for, the birth of the demonic sword is one of the best cultivation novels I have heard, and seeing a fanfic of this type filled me with a lot of excitement, but As I said, there are negative things that could have been better, which I already mentioned. Good luck with your fanfic if you continue it, I say this comment with great respect and without the intention of offending, it is only a brief review of what I think of your work.