Source: Bestiary 5, pg(s). 286
A grown zygomind resembles a cage 25 to 40 feet in diameter, can reach a height of 500 feet, and weighs around 40,000 pounds. Its mycelium can stretch for 10 miles, comprising hundreds of tons of biomass.
Zygomind spores float in space, spreading their mycelia where there are intelligent creatures. As a young zygomind grows, non-intelligent creatures like animals will start to disappear, followed by intelligent creatures that track their prey to the zygomind. Days or weeks later, these creatures become undead, infected with a desire to bring ever-greater intellects into the zygomind. After a few months, a zygomind can exterminate a small city.
When a zygomind grows large enough to be visible above the treeline, its psychic trap is usually sufficiently developed against any resistance that intelligent creatures can mount. When investigating a zygomind, they are frequently sucked into its mindscape without realising, all while their real body mindlessly moves towards the zygomind, which then proceeds to effortlessly absorb their nutrients and turn them into mindless undead. The mindscape becomes more and more convincing as the zygomind absorbs more prey, and entire armies assaulting a mature zygomind have halted their march to slowly offer themselves to it, all while thinking themselves victorious and returning home to live long lives.
Zygominds can be tracked by knowledgeable adventurers, usually from the presence of undead whose victims always wander off in a certain direction, a sudden spike in sleepwalking, or lumberjacks disappearing en masse into the woods. However, tracking a zygomind's enthralled victims is very time-consuming due to their incredibly slow speed.
It is impossible to shake off a zygomind's victims from their torpor, except with powerful psychic magic, but such an act will draw the zygomind's retribution. Adventurers have been known to willingly submit themselves to the mindscape, where they have to undertake the monumental task of convincing previous victims that they are living in a false world, before their real bodies reach the zygomind to be consumed.
Those that have had previous contact with zygominds are advised to be always aware if they are still living in the real world or not. Psychic magic or those familiar with mindscapes can be used to verify this, but the zygomind can also create such illusions to deceive victims into thinking that they are free.
When a zygomind is destroyed, it explodes in a cloud of spores that typically return to space and seek for intelligent prey on other planets.