Hastur is a Duke of Hell who becomes trapped in an answering machine. He later escapes when a telemarketer phones, and promptly devours the entire staff of the telemarketing office (unintentionally spreading a "wave of low-grade goodness" throughout the population). Hastur is generally accompanied by Ligur on his journeys to Roundworld and is the taller of the two.
On Roundworld Hastur (The Unspeakable One, Him Who Is Not to be Named, Assatur, Xastur, or Kaiwan) is a fictional character in the Cthulhu Mythos. Hastur first appeared in Ambrose Bierce's short story Haïta the Shepherd (1893) as a benign god of shepherds. August Derleth, who came after Lovecraft, attempted a new vision of the Cthulu Mythos where the unspeakable gods of old, who would have far predated Christianity, became the reference points for Christian evil and Satanism. Lloigr, formerly a group noun for a whole race of demonic beings (interestingly, eponymous with the Welsh word for England...) becomes a single discrete Demon. Hastur is given pride of place as one of the dreaded Ten (Dukes of Hell), who may be summoned by Satanists at the Black Mass using a formula later written, in full, in Shea and Wilson's cosmic trip Illuminatus!.
Lloigr = Ligur as Hastur's sidekick....
Illuminatus! uses the almost Bursar-speak mnemonic A boy has never wept nor dashed a thousand kim to idenify the Ten Dukes of Hell, who are Asmodeus, Belial, Hastur, Nyarlathotep, Wotan, Niggurath, Dholes, Azathoth, Tindalos and Kadith.
After devouring the telesales people in an unspeakable and totally justifiable manner, Hastur performs the equivalent of burping after a really good dinner and says, to an empty room full of skeletons, "I needed that." In Michael Moorcock's Jerry Cornelius stories, when the Big Bad manifests and devours somebody, he remarks to the empty air "A tasty world."