The schematic to synthesize these darkened vombata appeared as a reaction to the invasion of the Mawsworn. The resulting vombata look different--darker, much like the invaders--but do not appear to behave any differently.
The Enlightened revere all of the First Ones' creations, yet for many, the vombata of Zereth Mortis are above the rest. These creatures are equal parts trusted beast of burden and beloved companion.