Descension

Magic has affected the species and people of what is now called Sunken Earth differently. Most people and species experienced no changes to their bodies, constitution or minds. Some lucky ones have gained new powers, abilities and more. Even fewer unlucky souls have what has become known as Descension.
Named after the sinking earth itself these unlucky ones have found their bodies or minds ailing because of its proximity to magic. Symptoms range all over, often masquerading as other diseases or illnesses, with two of the only common symptoms across most (not all) suffering being a slight blue tint to the white of their eyes and a slow degeneration.
While no cure has been found resources abound for those who contract it. Underground medicine and spells are manifold and Starmark and the other larger conglomerates have a variety of medicines for those who can afford it.
For some descenscion feels like a gift and prophets have arisen, calling descendants blessed and chosen. This nascent faith has a very slowly growing population, largely filled with people afflicted looking to find solace in company, and bolstered by the rumors of descendants miraculously cured of their disease. While a national movement has yet to take shape, local populations (especially in big cities) are growing.

Descension is a slow, degenerative disease affecting all species on Sunken Earth, seemingly random. No pattern of infection (or genetic condition) can be found, nor a pattern among symptoms or speed of degeneration (aside from the blue tint to the eyes). Because no pattern has been found there largely is no stigma related to the condition, most people know at least one person afflicted, and descendants are free to carry on normal lives without fear of reprisal or outing. The one large caveat to this is Starmark and other corporations are slowly introducing legislation preventing descendants from getting health insurance. While a new movement among the hyper-elite, it has already begun a loud and continuous stir.
It is up to the DM, or PC's to decide which among their party and which NPC's are afflicted, knowing that (depending on who you talk to) between 25 and 35% of the population have it).
Those afflicted will need to make a saving throw of their choice between Constitution, Wisdom, Strength or Dexterity (based on what the PC chooses as their main symptom of Descension) every other long rest, or a semi-regular period of time defined by the DM. Failing saves will have the chosen stat either reduced by 1. There are a variety of magical and technological medicines that are widely available that can (depending on the difficulty or worldbuilding) can give advantage on these throws, add a static modifier, or prevent them all together.

Type

Magical