A few points that are not spoilers, or were answered in the update already out on patreon that will be released for free soon so I can answer freely. (You will forgive me my little plug
)
-Demons and devils are different things. Demons came from another plane, where they did fill a similar role than demons. But in the plane the story happens, devils are led by Asmodeus. He is more...how to say that...reasonable than his demon counterpart, and more importantly, more intelligent. He knows that if devils are known to not respect deals, no more deals will be made. Of course, like you say it's a monkey paw, but a lot of people think they are cleverer than they are and still make those deals. Some mortals are more clever, and get the better end of the stick.
He also views mortals as resources. And you don't kill all your cattle at once or you starve...something demons did not do. They also have a more monstrous side. While some look mostly human with difformities, others are behemoths of incredible strength.
As for demons power and limitations, the MC and most of the people in the story are not aware of them yet, so I will not expand on that.
-Wood elves and high-elves are related, but different races. They consider themselves as such, it's just that humans see pointy ears, elves. Wood elves have powerful magic, but the druidic type. Not as useful in combat, but you do not enter their forest uninvited and leave unscathed.
Aetas rule the open field, where their battlemages and heavy cavalry cause terrible losses to massed troops."
Wood elves rule the forest, where their druids can manipulate nature to transform it into a deadly trap and their skirmishers can vanish like by magic.
-Naesala was salvage because the merchant did not have an heir. If she had, she would have to be returned to them. Not for the goods in the cart, something found in the wilderness unattended, undefended, is free game. The brand, when the Master die, do not disappear, but is inactive. The family, if they do not have a mage, would have to hire one to make the transfer. Some mages are specialized in that sort of magic, there is a position at the court that is called the Master of the Brands, the leader of the condemned. (see below.)
-You are perfectly right about the different ranks of slaves. Personal slaves are the equivalent of a footman, someone who is very close to their Master, and is generally viewed as above the others. Like your example, when a Greek educated slave would often be viewed as part of a Roman family, and freed when the Master died, there is Martha. She enjoys the total confidence of Athagan, and she would just have to ask to be freed. She does not because the brand affords her some advantages, like an improved resistance against mind-corrupting magic, and the ability to be tracked if something happens to her. She is also viewed with much respect around town, because of her skills and because if you fuck with her, well, the big bad battlemage makes you dust.
-in Aetas, collaring someone is reserved for crimes that would warrant the death penalty. They are mostly used in the condemned, shock troops used as "cannon fodder". It does give them a chance to be redeemed. While the normal brand can be erased, the collar cannot, when forgiven it turns white. One character is such an individual. Who? Who knows...
Collaring someone who do not deserves it is punishable by death or...collaring.
-Athagan's slaves are loyal because they cannot lie. It is incredibly easy to root out a spy or a saboteur if they cannot lie.
Regular interrogations are part of the life of the slaves of the most paranoid Masters.
Their resistance against mind-altering magic also helps.
Their loyalty come also from their good treatment. They are well-fed, treated with respect and not forced to have sex with anyone, they are basically servants with a brand. And he is protective of them. In a dangerous world like that, it is an appealing prospect compared to tilling the soil where a monster can come out and eat you alive...or worse.
I love world-building, it's my favorite part of it. I try to create a world that makes sense. That one, excluding the sexual elements, is actually a world that I used a lot in tabletop RPGs. As such, it was well tested by my players, who love to find those cracks, the bastards
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Of course, I let a few things pass, and sometimes, something that does not make sense happens. I am just human after all.
But the advantage of a fantasy world is that you can always bullshit with: "it's magic"!
I try not to though, I found that a world with a lot of verisimilitudes is more engaging.
On that, I am going to work on the update.
