The ziidroni /ˈziːdroʊni/ is a dark stranger with pale, xanthous eyes and gums, with additional tinting occurring on the limbs. Its skin is thin and brittle, and separates from its body with ease, revealing fibrous flesh which hardens upon exposure to air. It possesses only a small, shriveled unidentifiable organ within its stomach region, with this organ appearing palm-sized and atrophied in 45% of individuals. The ziidroni smells of greasy metal and burnt rubber.

The ziidroni appears primarily in boiler rooms, pipe-filled basements, and other windowless, industrial areas. It very rarely appears in apartments and other residential areas, and only in rooms which receive no direct sunlight (whether this is due to heavy curtains or an absence of windows). Cramped and cluttered rooms, low ceilings, and scattered papers and trash appear to raise the likelihood of a ziidroni infestation.

The ziidroni's skin and flesh appears in the air in sheets and fragments, like rust turning to flesh. It forms completely within seven minutes, but remains still for several hours after generation until it begins moving with a pained twist.

Just over a quarter of individuals do not fully form, and instead, after several hours of half-formation, break apart into a black powder which disappears upon contact.

The ziidroni possesses a contentious and agitated disposition. It is not capable of ambulation, and appears locked into its point of generation, where it remains suspended at a height of five to six feet. During the early stages of its life, the ziidroni twitches its hands and jerks its head back and forth with a jagged spasm. Its jaws appear locked in place at an acute angle, and the ziidroni can move them only slightly, its tongue flitting forward only to get caught on its sharp and uneven teeth. It grates its claws across any nearby object, destroying whatever part of its environment it is able to reach.

The ziidroni is prone to random contortions, with its arms or neck twisting back or its tail twisting up tightly around it. While initially, the ziidroni is able to pull itself back into position (albeit with a wrenching pull of its appendages), over time, the ziidroni's body grows more and more twisted and kinked, and it becomes locked into these gnarled poses. Cinched into agony, it begins to engage in self-injurious behaviours, and rips at its own skin or claws at the flesh beneath. As the ziidroni ages, its motions grow slower and more pained, although it retains its seething hostility toward both itself and its surroundings.

In addition to this progression of contortions, the ziidroni's teeth also grow in number over the course of its life, and eventually crowd together and break. This breakage appears to cause the ziidroni a considerable pain, its breath turning shallow and hoarse.

Although new skin does spread out to cover its injuries (both self-inflicted and as a result of its frenzied contractions), sloughed-off sheets continue to hang downward, turning hard and dark in color, further distorting the ziidroni's form. As it becomes more twisted, its speech becomes softer and more terrified in tone, and its syllabic repertoire grows more limited.

Despite its lack of mobility, the ziidroni is aggressive, and always attempts to attack any sensitive who comes near it, swiping its arms forward and slashing with a vicious enmity, its voice gnashing. While its limited range prevents it from posing too much of a threat, a young ziidroni is nonetheless quite strong, and able to tear flesh down to the bone with its crushing grip.

During the early stage of a ziidroni's life, its proximity has little effect on sensitives, aside from its presence causing a faint hoarseness of the throat or an involuntary twitch of the index and middle fingers. As the ziidroni grows more crumpled and distorted, however, so too does its effect upon sensitives increase. Joints become stiff and lock up, and each jerking contortion of the ziidroni's form causes further rigidness in the sensitive's own body.^㇍

By the time the ziidroni reaches old age, its body is capable only of infrequent jerks and trembles, emitting no vocalizations save for a strained droning whine. It dies with a final twist, as though wrenched in the hands of an unseen giant. The ziidroni's corpse continues to hang in the air several weeks after death, but grows exceptionally brittle during this time, until a gentle touch causes it to peel apart into thin black fragments, leaving behind a pile of dark, ashy flakes upon the floor below.