Rampant Forms

Species that has been effected by archaeotech nanobots operating on the Everchanging Dyson Sphere. Some rampant forms keep control of their body after being morphed but some do not. The ones that keep control of their body remain sentient if they were before. Sometimes they might not even know they went rampant, even with the symptom as obvious as drastic modifications to ones body.  After transformation, they will become semi-immortal. 
Some can reproduce, but most cannot. Their offspring will most likely not resemble either parent in any way. There are some that do however.
 Some grow large appendages, others grow a thick carapace armour, and all are modified in odd ways. Some grow ranged weapons such as cannons or bio-plasma cannons. 
The Hyperion Federation speculates that, should they manage to find out how exactly (and why) the nanobots do this, that might be key to understanding most Rikavi Ancients technology. Of course, though, archaeotech is very difficult to understand so the HF are unsuccessful in that endeavor. 
Although the cause of rampancy (the nanobots) can be easily destroyed with EMP, rampancy itself is not fixed with EMP. 
Rampant forms tend to learn their environment in much detail. They know all trap locations as the nanobots add that information in themselves. This is updated in real time, as the terrain of the underground layers are constantly modified. 
Some rampant forms have been known to defeat HF ground military, forces. Such as Revenant MBTs despite those being extremely large and heavy. Some vehicles can also be modified. These will be modified in ways dissimilar to biological ones, yet still significant. In rare cases, the vehicle and its crew may merge into a single biomechanical entity. These forms are notoriously difficult to defeat. The hf are however particularly curious about these, so returning one to them will earn a lot of prestige. 
They can use several means of sensory perception. Often visual, sometimes thermal, or even psionic sensory. This allows them to find hf scientists or other explorers even though walls, doors, traps and so on. 
Many can also fly but this depends on what the nanobots wanted to do at the time. Entities that initially could fly before being rampant sometimes would no longer be capable of flight, others would be constantly flying and having no way to land safely. Some lost hf scientists became flight capable after being infected.
As there is little else to eat on the ever changing Dyson sphere, they eat other rampant forms. This was intended by the artifact on the lowest floor, though they prefer outsiders as a target. Outsiders tend to be less well defended.
As such, they are to be engaged with extreme prejudice and care by all HF forces and scientists.