Halfdaemons

Halfdaemons are a result of sexual intercourse (consensual or not, and that goes both ways) between a human and a spirit (almost always a daemon, hence the name). They are rare outside of the Lost Lands, and barely more common inside them. While there is a sizeable number of them getting born every year, they are too thinly spread throughout Karadia.
As a result, there are almost no halfdaemon 'societies'. This means that while powerful, they are also rare and have no way of self-perpetuating their own existence. Such halfdaemons end up marrying normal humans, which results in more humans down the line - but no new halfdaemons, unless the circumstance of their birth is repeated.
Due to the 'while powerful' part they are seen as valuable commodity and often offered to join various imperial organizations regardless of their social strata. Most halfdaemons are born with natural talent for magic (especially some types of those), often also a powerful physique and some other gifts and abilities. On the other hand, when their magic is of the bad variety, they can easily become the Grand Empire's worst nightmare.
This leads to being born to some of the halfdaemon subspecies a case of blessing that's dangerously close to being a curse. The fact that not all of the daemons responsible have any idea how does family work (which ends with many halfdaemons being brought-up by a single parent - or worse) doesn't help.

Basic Information

Anatomy

As a rule, they greatly resemble humans - just magically altered. The magically-altered part is a double-edged sword - while half-daemons have an inborn magic talent and (this seems to depend on how powerful their supernatural parents were) some supernatural abilities, they are all vulnerable to dedicated anti-magic measures.
Half-daemons are massively weakened by silver and cold iron, easily killed by the antegnite (few minutes of contact through the skin is enough for most of them to drop dead), and can be kept severely weakened by such a simple thing as a line of blessed salt that they were made to cross to enter another room.
This is primarily because their magically-altered part gets weakened or damaged by those means, and its tied to their bodies on very fundamental level. What banishes daemons can cause a total organ failure in a significantly more material half-daemons (simply by taking their supernatural half from the equation).

Biological Traits

Subspecies

Amalthians are a relatively rare end-result of a sexual intercourse (non-consensual in most cases) between an aberrant (supernatural servant of one of the resident eldritch abominations) and a human. They are born with a various degree of form damages (and that's when the form of their mother has resisted the damage during the encounter, as otherwise - or if their mother was the aberrant - they are born as aberrants rather than amalthians). A
malthians are known for astounding talent for magic and high form resistance (and form regeneration, even if limited), together with some special abilities tied to their supernatural parent - for example children of the Watchers tend to possess supernatural sixth sense for magic and a type of 'evil eye'-style ocular inborn ability.
Unfortunately those that do not go through a long and painful purifiction ritual of the Imperial Cult during their early childhood almost always give in to their eldritch half and turn bad. Very bad. Even with such rituals, there are many amalthians who are simply too damaged to live in the 'wild' - after all, it's hard to live among others when you drive them insane merely by being seen.
Such broken amalthians are often allowed to live their lives in various sanctuaries of the Imperial Cult, doing menial work or even becoming priests, however ones that never leave their sanctuary.
Berserians are a result of crossbreeding between daemons of the Nine Hordes and mortals. Which happens both consensually (especially between the daemons and tribesmen following the Nine Hordes creed) and not at all (Nine Hordes does a lot of raiding, after all). The result are berserians - humans who are best described as supernaturally strong and resilient. Average berserian can survive superhuman ammount of punishment and is way stronger than human average (they also tend to be rather muscularly built).
All berserians also have an inborn ability to trigger berserk rage at will (it improves their strength and resilience even more, although also makes them uncontrollable), As a result, the non-Nine Hordes ones are quite commonly seen among both the local militias, adventurers and criminals.
Devians are probably the most common of the halfdaemons, born from the unions between humans and the servile daemons of the Rapturous Ecstasy. They are most likely (of all the half-daemons) to be a basis of population of something, primarily due to how interested in sex are the servants of the Ecstasy (at least those of the Procacitas).
They are known for two things. The first one is that they are - by rule - either very or even extremely beautiful/handsome in a rather beautiful way. The beauty comes alongside the increased (when compared to baseline humans) libido.
The second is that they are quite likely to not conform to traditional human division of sexes - they are many devians that are hermaphrodites, many that are extremely feminine males and many that are biologically asexual. They also tend to have inborn talent for magic (especially the one of the Ecstasy), and quite commonly dislike their own nature (if only because of the way they are seen in the imperial culture).

Genetics and Reproduction

They are magic-altered humans, meaning that they can breed with all humans and a lot of non-humans (as all humans can). However their supernatural half is inherited separately from genes - and in fact is almost never inherited, unless both parents are half-daemons of the same subspecies. This results in a generally small number of actually halfdaemon communities - this is achievable only in the petty empires of the Lost Lands, where daemonic servants of the hierarchs walk alongside mortals every day and night (and have interbred with them for centuries). However even there the half-daemons are relatively rare.
It also has to be mentioned that not all children of human-daemons are half-daemons. A lot - if not most - of children from such unions are simply daemons. As an unofficial rule, 70-80% of children of human mothers are half-daemons (the rest being daemons), while if the mother is a daemon 70-80% of the children will be daemons (although this category seems to have a notably larger variation - spirits work differently, the pregnancy has little to do with biology and they have enough control over what's inside the body to make the ratio more of a personal decision than a rule).