Hi there, author here. I just recently read a book where the author had one of these chapters in their auxiliary volume, and I thought that was a great idea. So here I am, debating what to write and what to not write, what contains spoilers and what does not... If you really do not like spoilers, even the tiny littles things, you can read down to the third point.
First off, I would like to say that this novel aims to be quite dark, not entirely like Shadow Slave, for those who've read that. I don't wish for you beautiful readers to get depression. For me, a darkish novel contains many parts where gore is necessary, such as in the depictions of torture, executions and other bloody things. During the development of my story there will be times where gorey things happen and I will not shy away from describing them.
Secondly, the pace of the story will be rather slow, as I like to really bolt down the foundations, possibly, the story will quicken up the further I get, who knows?
Thirdly, there will not be any harems. The story follows a human boy so human traditions of the modern standard will apply. This does not exempt the possibility of other individuals in the story creating their own harems, but MC will not.
Fourthly, the power system is centred around a global energy called "Fabric of Magic", where different races have developed affinities and interpretations of said system. This will be further explained in the second auxiliary chapter. Every individual with magical strength posses a "Saints sense" or "Saint-sense" which grants them the ability to detect vibrations in the Fabric of Magic, essentially what creates spells. Think of it as a 6th sense where the user gets the ability to "see" spells before they are casted and allows for the option to dodge. Anyone not having magical abilities do not have the Saints sense. The name Saint sense originates from a person long gone that discovered the ability and named it after herself, therefore Saint sense.
Fifthly, the setting of the novel is in a medieval timeline. The societal structure is similar to the feodal but otherwise not in unison with typical medieval thingys. Due to the medieval setting, war and battle will be happening according to known methods from our worlds medieval time.
That should be the end of what I wish to write here, see you in the comments hopefully!