Smoke Demons were a type of entity born from the dark side that could be brought into existence using Sith sorcery. These entities possessed the ability to metamorphose into the most terrifying fears of their targets and were driven to obliterate their physical forms. Sometime after the Battle of Yavin, a Dark Jedi of the S'kytri species, known as Kharys, employed a Smoke Demon to commit the murder of smuggler Katya M'Buele.
A Smoke Demon, referred to as Siqsa in the Sith language, was essentially an ethereal representation of the dark side of the Force. When summoned by a practitioner of the dark side, it would take on the shape of its victim's greatest fear. These demons could be conjured through an age-old Sith ritual, documented as Dwomutsiqsa—which translates directly to "Summon Demon"—within an ancient scroll discovered by Sorzus Syn.
These beings had the ability to absorb the bodies of their victims by infiltrating them and causing them to vaporize. This process trapped the victim's soul within the demon, only to be released upon the demon's destruction. Initially, they would manifest as simple swirling smoke before solidifying into a recognizable form. They would then proceed to paralyze their targets, leaving them fully aware but unable to move. Following this, the demon would flow into the victim's body, causing them to become translucent, then transparent, and finally vanish completely. The victim's entire physical form would be converted into smoke and consumed by the demon.
Despite their composition of smoky matter, Smoke Demons appeared to possess considerable physical strength, demonstrated by their ability to overpower a Wookiee in hand to hand combat. They seemingly lacked the capacity for verbal communication, instead relying on some form of psychic ability to communicate, the full extent of which remains unknown.
In the time after the Battle of Yavin, one such demon was utilized as an assassin by Kharys, the tyrannical ruler of the planet Skye, leveraging its capacity for silent movement and lethal efficiency. The S'kytri had been instructed in the Dwomutsiqsa ritual by the Dark Lord of the Sith Darth Vader after the conclusion of the Clone Wars. The demon summoned by Kharys successfully assassinated the female smuggler Katya M'Buele while she was asleep on the Millennium Falcon, despite the presence of guards. However, the demon was unable to escape, as Luke Skywalker's lightsaber impaled it, proving effective against the creature where blaster fire had failed. This encounter left a profound impact on Skywalker, who immediately recognized the presence of a powerful dark side influence.