The odds of a given planet developing life are astronomically low. But on an astrological scale, astronomically low odds produce results a plenty. Yet it is a truly rare thing for life to escape and outlast its planet of origin.
The Hive achieved intergalactic status not by evolving the innate ability to leave their home world or the intellect to substitute, but by developing a path of adaptation capable of taking it from another species. The Novus found the home planet of the Hive, and the Hive left for the stars.
Eons pass and the Hive exterminate or are exterminated, only for the scattered remnants of their species to be discovered and revived by future civilizations. Like indefinitely slumbering seeds spread across the universe, the Hive wait to be unknowingly found again.
Society: Hive possess the intelligence of whatever species gave them form, and any assimilated individual retains its knowledge and identity. But the ego of the hive is encoded into every cell.
Nothing is more important to a drone than the desires and needs of its queen. And the cultural beliefs of the queen shape the drones that follow it.
Depending on the individual that becomes a hive’s queen, the Hive may behave like vicious predators, cautious animals or even Novus. But the hunger of their queen and necessity to sustain egg production shapes the goals of every Hive.
Ecology: Hive reproduce through parthenogenesis, each hive of Hive (yes, we know it is confusing) is centered around one queen served by starile drones. The queen remains nearly immobile, anatomically specialized for one of the two roles it fills in the hive.
A satiated queen is in many ways a true monarch (if a stationary one), directing its drones towards its interests, ambitions and often entertainment. But the rapid production of hive eggs a queen is capable of demands constant nutrients.
If a queen is denied food, its production will slow accordingly. But this is accompanied by a constant clawing hunger that grows the more the queen’s production reduces.
A queen suffering from hunger will drive its drones to seek food at any cost, eventually risking the hive to alleviate the suffering.
Appearance: Hive have the shape of creatures they assimilate, but that is where the resemblance starts and ends. Leaner than the non-Hive equivalent, many appear as a nightmarish visage halfway between insect and skeleton.
Game Play: The Hive give mechanics to the more biologically infectious hive mind, one that does not destroy the self entirely but slaves it to the desires of an alien life form.
The rules presented above are heavily inspired by a popular species of endoparasitic aliens from a successful media franchize. However, the same mechanisms can be used for a wide variety of infectious hive minds.