The origins of the araclathrus are mostly lost to history, as no sentient life remains from their origin to recall how they came to be, save for the fact that they were crafted by mortal hands. What that creator was thinking, why araclathrus was needed, or what purpose they were to serve are unknown questions. What is known is that araclathrus can be found lurking around asteroid belts and have been known to grow from simple fungus collected while passing through nebulous dust clouds found during interstellar travel.
Araclathrus consume inorganic material, like rocks and heavy metals found in asteroids but also the hulls of spaceships, and when they have consumed enough, they simply bud and pop smaller araclathrus from their bodies. Sometime, a single araclathrus will not bud and grow larger, sometimes becoming the humanoid sized or larger. It is unknown as to whether or not this is a conscious choice or an environmental stimulus response. Planets that have araclathrus make landfall find them nearly impossible to remove due to their fungal nature, and they cause endless trouble in their consumption.
In their fungal form, once a colony of the fungus has collected and grown, the araclathrus appears deep purple and green with a moss-like texture, save for the opalescent spikes piercing out through the moss. These spikes grow in number from a single spike up to eight as the fungus matures, and when the eighth spike has reached its full height, the araclathrus takes its spawn form by converting much of the fungal material into a cytoplasm which provides the internal structure for the araclathrus. This spawn resembles an arachnid creature covered in the same purple-green moss but it does not have eyes and its legs sprout from all around the central body, leaving the creature without a discernible front or back save for the mouth on the underside. The speed at which the spawn forms depends on the richness of the material on which the fungal colony forms. This process happens faster on asteroids than on the metal hulls of spaceships.
Araclathrus stat blocks and abilities can be found in the upcoming Galactic Primer on Natural Environments, one of the rewards of the Spaceships & Starwyrms Kickstarter launching on April 25.