The Astral Plague (AKA Space AIDS, AKA The Hubris) is a condition caused by exposure to Astral Energy. Despite the comparisson to AIDS, it appears to have more in common with radiation sickness, or perhaps cancer. It is best known for wiping out the Ytaran civilisation, but it has recently afflicted The Party during their adventure in Ginaron.
Those afflicted with Astral Plague are forced to make regular fortitude saves. The DC of this save is unknown, but it is greater than 13. On failure, the afflicted takes a point of constitution damage. Without treatment, this is of course soon fatal.
It is possible for spirits to protect mortals from the Astral Plague, although there is a range limit. It is also possible to remove the Astral Plague from a mortal using a large amount of Karma. Daggerface is also inexplicably immune, the reason for which is a topic of much debate.