The conjuring of spirits had been a staple of the Western ritual magic tradition for centuries, works like the LEMEGETON CLAVICULA SALOMONIS focusing on the invocation of angels, demons, etc. A resurgence of interest in occultism accompanied the overall increased interest in spiritual matters in the late 19th/early 20th century, coinciding with the Third Great Awakening in the United States and the rise of Spiritualism in English-speaking communities. The late 19th century saw the founding of the Theosophical Society, the Hermetic Order of the Golden Dawn, and the Society for Psychical Research, and the publication of works like The History of Magic (1860) by Eliphas Levi and The Book of Black Magic and of Pacts (1898) by A. E. Waite helped popularize material that had previously been largely unavailable to the general public.

Cults too have a long history in European history and literature, from various religious sects to secretive fraternal orders like the many forms of Freemasonry; colonialism brought Europe into contact with the manifold religious organizations and societies of the world, which were usually poorly understood and quickly exoticized. Sir Arthur Conan Doyle's first Sherlock Holmes novel, A Study in Scarlet (1887) for example, gives a very skewed and inaccurate picture of the Church of Latter-Day Saints. Other very influential literature along this line included Là-Bas (1891) by Joris-Karl Huysmans, about Satanism in France, including the famous depiction of a black mass.

So by the 1890s you start to have this increased interest, awareness of, and available of mystical and occult writings, and you have a great deal of information coming in about cults, sects, and secretive groups of all sorts - from fraternal orders like the Hermetic Order of the Golden Dawn, to tales of French Satanists, to the Thugs suppressed by the British in India during the earlier part of the century - all of whom made great material for fiction. The third part is a little trickier to trace: the idea of forces or creatures from outside which are not specifically drawn from existing occult or religious material.

The Industrial Revolution and rising awareness of science had begun to give form to new, more nebulous horrors than vampires and werewolves: "The Horla" (1887) by Guy de Maupassant, "The Damned Thing" (1893) by Ambrose Bierce, "Oh, Whistle and I'll Come To You My Lad" (1904) by M. R. James, "The Willows" (1907) by Algernon Blackwood, "The Gateway of the Monster" (1910) by William Hope Hodgson, etc. all deal with nontraditional creatures or entities which impinge on the normal world, but are not directly a part of it - they are the darker, agnostic counterpart to Spiritualism in a lot of ways, often unseen (or unseeable) entities that come from "Outside" in some fashion - whether that be another dimension or outer space is often left up in the air - and it's notable several of the stories have the deliberate mode of the ghost story, representing in many cases a kind of haunting, just from a nontraditional source.

Putting all these elements together was not something that happened right away; but in the early 20th century the dime novels gave way to pulp magazines, and in 1923 Weird Tales emerged, focusing on tales of the strange and unusual - and remained one of the few markets for adult-oriented fantasy fiction until it ceased publication in 1954. While there had been magazines like The Argosy and The Black Cat which had published some weird fiction, Weird Tales was largely alone on the market for fantastic fiction for much of its existence, with competitors being either weak (Ghost Stories, Tales of Magic & Mystery) or short-lived (Strange Tales of Mystery and Terror) until the creation of Unknown in 1939...and it is really in the pulps like Weird Tales where these disparate tropes would come together, in stories like H. P. Lovecraft's "The Festival" (Weird Tales Jan 1925), "The Horror at Red Hook" (WT Jan 1927), and "The Dunwich Horror" (WT Apr 1929).

Lovecraft was of course not alone in writing for the pulps, and it was through Weird Tales that he came into contact with fellow-pulpsters like Robert E. Howard and Clark Ashton Smith. Howard in particular was more influenced by scientific romance (Edgar Rice Burrough's tales of Tarzan and John Carter of Mars, H. Rider Haggard's Allan Quatermain novels, etc.) and adventure and historical fiction (like Harold Lamb), but he found success in selling to Weird Tales and Strange Tales, especially stories that combined a gritty, adventurous narrative with some weird or fantastic element - and so created stories like "Red Shadows" (WT Aug 1928), "The Shadow Kingdom" (WT Aug 1929), and "The Phoenix on the Sword" (WT Dec 1932), creating the field of American fantasy popularly known as sword & sorcery.

Lovecraft, Howard, and Smith were far from the only writers who had mystical cults or wizards and sorcerers dealing with forces from Outside; and after the death of Howard in 1936 and Lovecraft in 1937 the tropes were picked up in part by writers influenced by those men like Fritz Leiber ("Fafhrd and the Grey Mouser"), Henry Kuttner ("Elak of Atlantis), and Manly Wade Wellman ("John Thunstone, John the Balladeer", etc.) Nor did any of these writers exclusively deal with mystical cults summoning weird monsters, but they carried on writing material which followed similar tropes.

Many of the pulp writers went into the comic book field during the 1940s, as comics ramped up and pulps wound down, and they brought with them the fantasy aesthetics that had informed their fiction. Gardner Fox, for example, borrowed heavily from Robert E. Howard in created "Crom the Barbarian" (1950) and later novels of Kothar: Barbarian Swordsman (which, ironically, were subsequently adapted into issues of the Conan the Barbarian comic book). Unofficial references to or adaptations of Lovecraft's material appeared in comic beginning in the 1950s as well. Fox also created the character of Doctor Fate for National Comics (one of the forerunners to DC), who premiered in 1940. Doctor Strange, who first appeared in Strange Tales (the comic, not the pulp!) in 1963 deliberately echoed this pulp literary tradition.

So...it's hard to point to one story as an "origin" or even first appearance of when these tropes came together, but the disparate elements really crystallized around Weird Tales in the late 20s/early 30s, and the enduring popularity of Lovecraft, Robert E. Howard, and their successors has gone a long way to its continuation in various media.