The creatures known as Nightmare demons were an almost mythical species originating from the planet called Droxine. These were small primate-like beings characterized by having two tails, fingers ending in suction cups, and a completely bald head that bore a striking resemblance to a Human skull. Nightmare demons possessed potent telepathic abilities, enabling them to induce madness in other beings through terrifying, hallucination-filled visions. Although it was widely believed that they had been exterminated some time prior to the Clone Wars, a number of nightmare demons managed to survive the widespread killing and subsequently fell under the control of the Galactic Empire. In the year 3 ABY, a surviving nightmare demon named Reist made an attempt to assassinate Rebel Alliance hero Luke Skywalker, but he was ultimately killed himself.
Nightmare demons constituted a species of diminutive, sentient primates, placing them within the same mammal order as Humans. Consequently, they exhibited an anthropoid form, distinguished by a torso supporting four limbs and a single head. Their bodies were covered in fur, and they possessed two tails. Their arms terminated in hands with four fingers each, while their feet featured only three toes. These fingers and toes displayed remarkable flexibility and were equipped with suction cups at their tips. In contrast to the rest of their bodies, the nightmare demons' craniums were devoid of hair, revealing what appeared to be an exoskeleton. Their skulls bore a strong resemblance to those of Humans, albeit significantly smaller, and their deeply set eyes emitted eerie flashes of light. Their small size allowed them to comfortably fit on a Human's forearm.
Beyond their agility and dexterity, nightmare demons manifested considerable telepathic abilities. They could penetrate the minds of other beings, incapacitating them with their deepest fears—hence the origin of their name. However, their telepathic powers had limitations, as they could be blocked by lead.
Nightmare demons originated and evolved on the planet Droxine, situated within the Esstran sector of the Outer Rim region of the galaxy. While not formally part of it, their homeworld was in close proximity to the Sith Worlds, the original heartland of the feared Sith civilization. Sometime between 3959 and 3956 BBY, the nightmare demons' planet became part of the territory controlled by Darth Revan's Sith Empire. It was widely believed that the nightmare demons had been completely wiped out prior to the Clone Wars, a vast galactic conflict spanning from 22 to 19 BBY and concluding with the proclamation of the Galactic Empire. Nevertheless, a small number of nightmare demons survived the widespread slaughter and persisted throughout the subsequent Imperial Period.
The nightmare demons that avoided complete annihilation were eventually discovered by the Empire, who paired them with elite assassins hand-picked by Palpatine, the Galactic Emperor himself. Those tasked with utilizing the demons' unique abilities were required to shield themselves from potential treachery by making the demons wear lead-lined hoods. Due to the terrifying mental powers they possessed, individuals from other species often exhibited fear and hatred upon encountering a nightmare demon, and the creature, in turn, could sense these negative emotions.
One of the surviving demons, a male known as Reist, was partnered with Altin Wuho, a Human replica droid who, by his very nature as a droid, was immune to Reist's telepathic abilities. Around 3 ABY, shortly after the Battle of Hoth, Wuho unleashed his nightmare demon partner upon Luke Skywalker, a celebrated hero and skilled pilot within the Rebel Alliance. After enduring a series of demoralizing visions, Skywalker managed to use the Force to overcome Reist's powers. Seizing his lightsaber, the pilot struck the demon in the chest, inflicting a fatal wound.
The nightmare demons were brought into existence by Steve Moore and made their debut appearance in his comic the Empire Strikes Back Monthly 149: Death Masque, released in 1981.