Greetings All,
KC has some...fetishes and fantasies that I don't agree with. For some reason he seems to favour forceful ladies. I think it partly stems from KC wanting to appeal to a large number of folks and their respective fetishes. Thankfully though this is mostly referenced as subtext and can be explained away in the setting.
From what I re-read of the base Mamono page they know a man's inner fetishes because magic and whatnot.
I'm going to summarize several of these fetishes that you mentioned to give an idea of what they're like and why KC included them.
In regards to the Dark Elf since I noticed you mentioned 'slave' and 'cum pump' those degrading terms are turn ons for some people. I don't understand it myself but, that is the case. Being put down and called names feeds into this whole 'master/servant/slave' relationship dynamic fantasy. It's actually one of the more common fetishes along with masochistic roleplays and BDSM. So I can see why KC included it here. But it doesn't go to the lengths that certain folks seem to portray it as being.
(After all he included the incest dynamic with the Devil Bug and the Dark Elf which I find steadily worse and abhorrent.)
Amazons and Hellhounds are of a similar but somewhat distinct fetish type.
The Amazon fetish feeds into the 'defenseless and sweet lover and passionate protector kink'
I.e things like "Oh he's such a cute little man, I should take care of him because he's helpless without me." This is another common fantasy and comes up in practicum courses often. This fetish comes from the desire to be both valued as a person and protected.
For the protectee the idea behind it is If a person is being cared for and protected by someone stronger than they are, that means they are valuable, or worth something to that person. (The protector) This in turn gives the protectee a sense of individual worth. It often comes people with low self esteem or ideas of lesser self worth as an individual.
For the protector the fetish is also about self worth but it comes from a place of caretaking or caregiving. This means that the protector gains a sense of identity and worth by becoming the both the 'Protector' and the 'Carer.' By looking after someone else who is in their eyes less abled they have a purpose and a role to play, they are given meaning and worth by taking care of another.
In healthy relationships where this fetish is displayed the two individuals rely on each other wholey, but they also have complete trust of each other knowing where the boundaries and limits lie. Over time both individuals gain a greater sense of worth and self identity as they work together and the relationship can evolve into a partnership where power is equally shared and equated to the newfound worth.
That is something KC surely missed out on.
Hellhounds also share the Protector/Protectee dynamic but it also mixes with the Dom/Sub fetish. Both are not mutually exclusive.
The Dom/Sub fetish again places quite a bit of trust in the hands of both individuals. The Dom must know the Sub's limits and tolerances while the Sub must be free to speak up if something has gone either too far or needs to go further while seeing to the Dom's own needs. It is a balancing of power that KC once again portrayed inaccurately as a unilateral power play on the part of the Hellhound. When it would be more accurate to describe the Dom/Sub fetish as a partnership of trust wherein both parties know the other's limits.
As for the copious amounts of Fanfiction displaying outright domestic abuse either verbal mental or physical the writers obviously have no grasp of the MGE or the fetishes in question. I would advise you as always to read those particular works with an air of caution and thought.
If you have any further questions feel free to ask.
Oh and my apologies if that was more Psychology than anyone was expecting, but it is my area of expertise and I love this setting and hate seeing it wreaked. (Even if some of the wreckage comes at the hands of its own creator. Damn you KC and your surface thin understanding of fetishes!)
Cheers,
The Weary TimeLord.