The Ebony Fleet ~ Undeath From Space

Their outlines were human, semi-human, fractionally human, and not human at all -- the horde was grotesquely heterogeneous.

H.P. Lovecraft

"Herbert West--Reanimator"

Deep within the depths of  the spaces between the stars sails the Ebony Fleet. These ships of a long forgotten alien culture are home to more then simple relics, artifacts, & treasures undreamed by modern space men. These doomed sailors of the stars also house microscopic, self-replicating robots that can invisbily build--or destroy--anything flowing within the atmosphere of these hulks. The reason they were created remains a mystery but they all are the fossilized remains of  some great space going fleet.Unliving vessels created millions of years ago now lost within the hyper space corridors of  many different universes. The citing of one of these ships is enough to send a colony of spacers in a blind panic.  Each ship seems to have a strange sense to crash itself into a world where the most life is & expend its deadly cargo of nanobots into the  air of a planet with the most life. A thin cloud of black dust is expelled into the air space surrounding the crash of the ship which slows down at the last second & hits the countryside with just enough force as a bubble of telekinetic power is created. 
  The process from the moment of impact is always the same.The nanobots  crawl inside your brain and set up neural connections to replace damaged ones. The nanobots are be able to rewire your thoughts. nanobots will be programmed to keep functioning after you die. They can form their own neural pathways, meaning they can use your brain to keep operating your limbs after you've deceased and, presumably, right up until you rot to pieces in mid-stride.
The nanobots will be programmed to self-replicate, and the death of the host will mean the end of the nanobots. To preserve themselves, they'd need to transfer to a new host. Therefore, the last act of the nanobot zombie would be to bite a hole in a healthy victim, letting the nanobots steam in and set up camp in the new host. Once in, they can shut down the part of the brain that resists (the cortex) and leave the brain stem intact. They will have added a new member to the unholy army of the undead.
  There are several empires that have several hundred to several thousand credits bounty on these fleets. There are adventurers whose sole occupation is to hunt down these fleets wherever they show themselves. Men who devote their entire lives to destroying as many of these diseased things as possible. Some however don't come back at all & become infected with the horror that resides upon these things. *


   *Use your  favorite zombie stats for these things & if your feeling especially nasty create variations on the standard zombie as you like