Transmission & Vectors
Every fomorian alive at the time their curse was first visited upon them was immediately subject to its full affects, as were many of their dead who were found wanting reaching back several generations. Any child born of two fomorian parents will inherit the curse without fail, every proposed example of an exception whether due to redemption or intervention has later been found to be untrue. Half-fomorians are not born with their curse but come into it as they age if their temperament matches their cursed ancestors, which has as-yet proven to occur for every known example who has been raised in their "society" and a large majority of those raised outside it. As the cursed blood is diluted across successive generations, the proportion of those who bear the curse decreases accordingly, but never entirely goes away. There are known cases of seemingly normal men with no fomorian heritage as far back as their family tree can be traced suddenly inheriting the curse due to a single millennia old ancestor if their temperament falls too far.
The fomorians were one of the greatest of the descendants of giants, and so among had one of the furthest falls at the conclusion of the War Against the Dragons. In seeking to reclaim their lost glory, they turned to horrific ritual sacrifice, cannibalism, and even worse to mortals they considered lesser. Not even the souls of their victims were spared their depredations. Scarring so many souls attracted divine attention followed shortly after by divine intervention in the form of the curse which is now better known by their name than they are themselves.
The fomorian curse is horrific both to experience and to behold: Limbs, extremities, and even spines are twisted at random. Perpetually weeping sores appear across the entire body and significant patches of skin necrotize. The eyes mutate and deform outwards, combining into a grotesque new organ less effective for sight and severely less protected from the elements. The pain is constant and nearly without peer.
There are no confirmed examples of the curse being lifted, though there are legends of such occurring, usually after some great act of penance is undertaken.