There are very few non corporeal undead in Urbe Mortuus. Most ghosts were returned to their bodies when the transformation occurred. It is also known that if the body of a ghost is taken there and interred in the soil, the ghost will be drawn back into it when it is reanimated provided the ghost has not yet moved on.
Some of those who return might see the removal of a physical form to be an advantage. Rogues of a stealthy bent (and significant skill) would find themselves returning as shades. In which case they would find themselves gainfully employed as hidden protectors or agents/spies.
If a fallen comrade is taken there and buried she will be given the same gift that all the denizens are given, she must however, remain in Urbe Mortuus or the power giving her life will cease to work. The form the person takes is based on her occupation. A spellcaster would become a lich (this may include priests, if said priests agrees to take the Dark Mother as his new deity), a strong warrior would become a skeleton.
As noted before the effects of the realms enchantment only extend to its borders, there is one way around this. If the citizen carries some of the soil with them, in a pouch or locket say, then they can extend there sojourn out of range. The length of the stay depends on the amount of soil transported. A coffin filled with soil will preserve a Urbein for one full lunar cycle, a small pouch will add another day. The unprotected length of time before the citizen dissolves is dependent on the strength of said citizen. (in game terms, if you are using a level based system the length would be one day per level.)
When the change took place, those that had been cremated returned as well. Their charred bones reassembled themselves and are bathed in an unnatural fire. They spend their unlife wandering around sending unlucky citizens to their final death or creating new ones. They are called Igneus Mortuis, or just Iggies for short, and are considered a scourge in the land.
Spirits who wander into Urbe Mortuus can attempt to seize control of one of the bodies of mindless undead, they can also travel about the place openly.