Shadow slimes were corrupted green slimes that thrived in the presence of shadow creatures. As with many other oozes, they clung to ceilings and waited for their prey to come to them.
Such slimes were almost impossible to spot, as they were always concealed. Even illumination from the lightspell did not reveal them. Only the daylight spell was able to reveal such foes.
As soon as shadow slimes detected movement, they would drop on top of their prey. They sucked the moisture and heat energy right out of their foes, damaging them and draining their power in the process. They could also damage items made of bone, wood, and leather.
Only fire-, sonic-, electric-, and sunlight-based attacks would cause damage to these vicious oozes. However, remove disease and deathward could also destroy patches of shadow slimes.
As well as dropping on their foes, they could extinguish light sources, and then shadow jump to their target.
↑The statistics block provided in the article gives an origin for this creature as "natural"; however, the body of the article itself clearly states its origin as the Shadowfell.