"The Waster uses a rather insidious disguise; they retain their hosts' clothing and overall silhouette, presumably allowing them to fool potential victims. The most immediately obvious change to their appearance is their foaming eyes and mouth that emanates a ghastly yellow light (similar to the hallucination Nicole from Dead Space 2). When the Necromorph is destroyed, the glow stops. Unlike all other Necromorph strains, which rely on their mutated limbs and abilities to murder their prey, Wasters attack their victims using a variety of melee weapons, including ice axes, picks, hatchets, saws, wrenches, crowbars, and police batons. While a Waster's body has almost no modifications to it, compared to a standard Necromorph, it possesses the unique ability to trigger further mutations on the fly; dismembering certain parts of their bodies can trigger horrifying transformations. When the upper body receives significant damage, the torso falls off, revealing three pronged tentacles growing out of the lower body. Upon dismembering their legs, projectile shooting appendages will sprout from the abdominal area for defence and also help with locomotion. Should the lower half of the body be destroyed, these same tentacles will spawn from the abdominal area from the upper body, though the existing arms will be used for movement, resorting to a crawl.
Rarely will this ever happen, but if both the torso and the leg have been shot off, then instead of dying, the Waster will sprout one more tentacle and rapidly crawls towards Isaac like an arachnid."
-The Dead Space Wiki