- You may also be looking for the planet Armus IX.
Armus was a malevolent entity created by an unknown race.
Armus was born as a by-product of a procedure in which a race of "titans" brought out from within themselves all evil and negative attributes that had bound them to destructiveness. The unwanted substance spread and coalesced into a dank and vile second skin. The race rejected this "skin of evil" and abandoned it on the barren planet Vagra II in the Zed Lapis sector.
Armus manifested as a black viscous liquid that could also assume a vaguely humanoid shape. Tricorder scans could not register the substance Armus was composed of. Armus was also capable of enveloping Humanoids and incorporating them into the liquid, where they would remain conscious while in liquid form. Armus was capable of then inflicting suffering upon its victims while they were in this state. Armus was impervious to phaser fire, and Data theorized it was, in fact, feeding off of the phaser energy. Captain Picard also assumed Armus was immortal.
After the initial abandonment, Armus was left in a state of undirected rage. However, when the rage was focused, Armus was capable of generating, around itself, an intense undefined force field. With this energy field, it was capable of blocking sensor scans, communications and transporters. It was also capable of using psychokinesis and teleportation on at least humanoid-size organisms within the field. Armus was also capable of inflicting energy discharges that caused synaptic damage to humanoids, killing them. Presumably, this field was also responsible for causing the nearby shuttlecraft 13 to experience a massive systems breakdown and crash-land on the planet in 2364.
Armus waited for someone to arrive for the rescue of the two shuttlecraft passengers, in order to sadistically torture them. After killing Lieutenant Natasha Yar with an energy discharge as she tried to walk to the downed shuttle, Armus expected to feel amusement. It also expected that the USS Enterprise-D crew would abandon the rescue effort. Even after they didn't, Armus realized torturing them would never be amusement enough. It wanted passage away from Vagra II, to find the beings that initially abandoned it there. Eventually, Picard was able to distract Armus long enough for the energy field to weaken to a point whereby it allowed beaming the shuttle occupants and Picard off the surface. Following the beam-up, the shuttle wreckage was destroyed with a photon torpedo to prevent any possibility of Armus leaving the planet, and Vagra II was declared off-limits. (TNG: "Skin of Evil")
According to Star Trek Encyclopedia, the race that created Armus was native to Vagra II.
According to Star Trek: The Next Generation Makeup FX Journal, the costume creation was divided between Michael Westmore's department (to design the head piece of the suit) and an outside company (to create the body). The head piece was made out of soft polyfoam with a latex skin over it. It was sculpted by Westmore and Gerald Quist. There was no oxygen tank given to Mart McChesney, so the scenes of Armus submerging and rising from the pit of black goo were timed with a stopwatch. There were three mouth holes on the head piece, designed in such a way that fingers could be easily inserted to clear the actor's mouth from the goo.
In the Special Features portion of the TNG Season 1 DVD, Jonathan Frakes explains that black goo was made from Metamucil and black printers' ink. In the FX Journal, Westmore explains that the body portion of the costume disintegrated during filming, after reacting with the goo, each day of shooting. According to Westmore, the goo was water-soluble methocel material and water-based black printer ink. Several more costumes were ordered from the manufacturer after the first of the two original fell apart. Westmore has not been able to find an explanation for the disintegrations, as the goo was supposed to be inert.