Morpholith

Morpholiths in their natural form were large pudgy figures, often built with two legs. Upon being created they would either take the requested shape that they were ordered to, or would naturally find a person to mimic in their environment.   Their body would shift to match their target and usually within a few minutes be indistinguishable from their host. Morpholiths could further shift their figure to different targets, this process would usually take twice as long.   Morpholiths that stayed as a particular target for long enough would slowly lose the ability to shapeshift, but became more and more anatomically precise to the target inside and out.   Enchanted onyx like glass orbs called corestones were implanted in the center of the morpholith which allowed a controller to see and hear what the morpholith could. They could also be used to give the morpholith instructions which it had to follow. Corestones could also be used to make the morpholith self destruct, which would also destroy the corestone.   If the morpholith was attacked and badly damaged enough, the corestone would break upon destruction of the morpholith.

Morpholiths were able to replicate aging appropriate to the species of their target, this even included dying of old age.

NEWLY CRAFTED: Newly created Morpholiths would either be given instructions on who to mimic, or would eventually find someone to naturally mimic overtime.
  Morpholiths could be wrapped in silk right after creation which would allow them to remain dormant seemingly forever until they were unwrapped. This allowed Morpholiths to be stored for future use. This was also how Morpholiths were uncovered and used in the 3rd and 4th eras.
  SHAPE SHIFTER: Morpholiths at this stage had selected a target to attempt to pose as and started to shift to visually blend as this person. This would be a rather quick process, taking less than ten minutes most often, before they would be visually identical. The closer the morpholith was able to be to their target, the faster the process would be.
  Sometimes morpholiths would be instructed to kill the target they were to pose as, and would enter the body of the person, usually while sleeping, and consume them from the inside out as they began to shift and resemble them.
  Morpholiths also had the ability to visually render themselves from memories people had of their target, but this process was very lengthy by comparison and sometimes had flaws. An example being if the person the morpholith was targeted as mimicing hadn't been seen by the person whose mind it had read in decades, the mimic would morph into the target, but would appear as young as the memories of that person, not the actual age of the target.
  RAW MIMIC: Morpholiths that had only recently started mimicing someone were still flawed in subtle ways. Memories would sometimes conflict, small discrepencies could be found, and even some behaviors would be different. These were often so subtle that they wouldn't be able to reveal the morpholith as a imposter, but someone with an intimate enough knowledge of the target might be able to discover the truth. During this stage morpholiths would be able to shift into another person if threatened or discovered, but this was usually a much longer process.   REPLACEMENT: After some time the morpholith had fully replicated the target and lost the ability to shape shift again. They would lose all memories of being a morpholith and as far as they were concerned they truly were their target.
  Orders given through the corestone could still be given at anytime which would take over the body of the morpholith. This allowed sleeper agents to exist in enemy ranks for years at a time.

Morpholiths had strong visual and hearing senses, but had no sense of smell or taste. In their newly created stage they also posessed the ability to read through memories of others to pull information about the person they were posing as, these would eventually be burned in as memories for the Morpholith.

2e: Morpholiths were created during the 2nd Era by the Duran-gahl empire. While their creation methods are lost to time, records show that it was a very expensive, delicate, and time consuming process. (Some theories claim that the Duran-gahl didn't originally create the morpholiths, and instead they were a product of early trans-universal raiding)   Originally planned as spies and assassins, the morpholiths unexpectedly proved much more useful and capibable in the field.
  3e: Towards the end of the 3rd era two morpholiths were discovered. The first was quickly destroyed by soldiers of Order of Balance upon discovery. The corestone of that one malfunctioned and did not self destruct upon death of the morpholith. This later allowed the order to construct modified corestones for use in Rot Tyrants.   The second was uncovered by the Order in 1435 3e, but was kept in it's container to be studied, but was stolen in a convoy raid by Echo rebels.