a Thesulac Demon is a type of hostile demon often referred to as a "Paranoia Demon", inhabiting the Buffyverse and being described as feared and insidious even by demon standardss : an unnamed Thesulac Demon would be featured in the Angel spin-off series as the main antagonist of "Are You Now or have You Ever Been".
Hyperion Hotel Incident
Powers and AbilitiesThesulac Demons possessed a number of abilities, largely telepathic in origin and were primarily emotion-vampires that fed on their victims to sustain themselves, they did this via whispering into a victim's mind and playing on insecurities until the victim was driven insane.
Thesulac Demons often haunted areas prone to having many humans, so as to play different victims against one another - while feeding the Thesulac Demon was invisible and intangible, much like a ghost.
Victims would go insane, commit suicide or perform violent acts such as lynching while under the effects of a Thesulac Demon.
When forced into manifesting into the physical plane Thesulac Demons were invulnerable to most attacks, save for large amounts of electricity and it was theorized (though never proven) that powerful weapons such as an axe may kill it.