Splitting from its ancestor, the symbiocrust has, as its name suggests, become symbiotic with the quefts of Mason. Infesting all current species and their descendants, it has a 98% infection rate, making a non-infested individual a rare sight. This is due to the fact the symbiocrust spreads via either contact between two hosts or via releasing clouds of spores from fruiting bodies, featureless stalk-like outgrowths, that form every few months. Spores that don't find a host will hibernate into the soil until they are warmed up by the body heat of a potential host. The spores will then quickly establish themselves and form a colony.
As they adapted to their hosts, they were forced to become "gentler" so that they would be given a better chance to survive and reproduce. As time went on, they began to they provide their hosts extra nutrients and vitamins they produce via photosynthesis in return for the nutrients they need. In order to prevent colonies of other symbiocrusts to form, they become rather devious and secrete chemicals into the circulatory system when they are still young. These chemicals tell the body how to fight off young symbiocrust colonies by the time the original one has established itself and matured, keeping it safe from the bodies defenses.
Besides providing for their hosts in terms of giving them the excess they create, they all block a good percent of the UV rays that bombard them within Mason's thinning atmosphere. Not intentional, this came about as they naturally protected themselves from the rays themselves as they relied on the sunlight that came with it for photosynthesis. Besides this, the size of a colony varies from host to host, though they tend to cover a good percentage of their backsides. What the future holds for this symbiotic relationship is as of yet to be revealed.