These ethereal creatures were able to shift between the Ethereal plane and the Prime Material plane at will, and thus could assume both an ethereal and physical form. Normally, an ethereal ooze would assume a cubic shape, much like a gelatinous cube. These oozes were flesh-colored, and parts of those that they had previously consumed whirled within them.
Such oozes could move through solid objects, but not force fields. As such, they could easily approach prey, and easily ignore their armor and shields. As they were mostly present in another plane, it was impossible to hear when ethereal oozes were approaching.
Ethereal oozes did not track victims in the Prime Material plane. Instead, they lurked in the Ethereal plane until they found large enough foes. Then, they assumed their physical form and attempted to smother the creatures. If successful, the oozes would try to etherealize their target, and then fade back into the Ethereal Plane, so that their target could not easily get away. Here, their potent acid would kick in, slowly digesting the creatures.
These creatures could only be harmed by magic weapons, spells, or regular attacks by other incorporeal creatures. As with other oozes, they were unable to become poisoned, polymorphed, put to sleep, paralyzed, or stunned.