The Cryptofictional Records Wing: The Moon Pool (A. Merritt, 1918, 1919)

All-Story Weekly, February 15, 1919, F.W. Small

On January 5, 1918, 33 year-old writer A. Merritt (Abraham Grace Merritt) saw his fantasy-horror short story "The People of the Pit" published in All-Story Weekly. This story describes the discovery of a city hidden in a remote area of Alaska, populated with tentacled creatures who worship an invisible monster of some kind. The protagonist, a man named Stanton, eventually escapes from the city, but is chased by strange "searchlights" emanating from the sky.

Six months later, in the June 22, 1918 issue of All-Story Weekly, Merritt's story "The Moon Pool" appeared. This story features a scientific party (one of them being a man named Stanton) coming across an unexplained, nefarious force near Papua New Guinea. This creature is somehow dependent on moon light and can travel along moon beams in order to snatch up its victims with paralyzing tentacles.

A direct sequel in 6 parts, "The Conquest of the Moon Pool" (published in the same magazine from Feb 15 to Mar 22 in 1919) combined the lost race concept of "The People of the Pit" with the supernatural horror of "The Moon Pool". In this much longer narrative, a group of adventurers enter the underground world and encounter a variety of strange races at war with each other. In the end, the surface-dwellers must save the surface world from an invasion from below.

G. P. Putnam's Sons 1919, Joseph Clement Coll

Later in that same year, "The Moon Pool" and "The Conquest of the Moon Pool" were published together in slightly modified form as the novel The Moon Pool, revised and with additional text added to the beginning of the novel. In this version the German antagonist Von Hetzdorp was also altered to become a Russian agent named Marakinoff.

Below are synopses of the original versions of "The People of the Pit", "The Moon Pool" and "Conquest of the Moon Pool", with images (mostly drawn by Virgil Finlay and Frank R. Paul) taken from various pulp reprints of these stories. Most of the images can be enlarged by clicking on them.

"The People of the Pit"

Amazing Stories, March 1927, Martin Gambee

Two explorers in the Alaskan north come across a mountain-range shaped like a giant hand. They see bizarre search beams and floating lights amongst the peaks. A ragged-looking man named Stanton appears, crawling on disfigured hands and knees. He tells the two men that he had discovered a giant canyon on the other side of the peaks leading to an ancient, alien city of flying, tentacled slugs, ruled by some kind of invisible horror. He had also discovered side caverns which then provided shelter from the tentacled glowing slug creatures. Eventually, the beings had captured him, but over several days he had managed to break his bonds and slowly climb back out of the pit, with each step being a mental struggle against the psychic pull of the creatures. After he relates this story of ancient, hidden horror, he dies.

Fantastic Novels Magazine, January 1941, Virgil Finlay

http://gutenberg.net.au/ebooks06/0601991h.html

https://archive.org/details/Amazing_Stories_v01n12_1927-03_AK/page/n51/mode/2up

"The Moon Pool"

The Throckmartin Mystery: The narrator, a botanist named Goodwin, remarks on the disappearance of his friend Dr. Throckmartin's expedition to the island of Uschen-Tau in the Ponape islands group (in the Carolines). In the face of romor, Goodwin decides to relate his own encounter with Throckmartin three years ago, before his disappearance: While journeying from Papua New Guinea to Melbourne on the Southern Queen, Goodwin runs into his old friend Throckmartin. However, Throckmartin seems to be a changed man, his face marked with a combination of horror and rapture.
Down The Moon Path: That night on the deck, Goodwin and Throckmartin see a moonlit path on the sea, and within it a strange glowing form accompanied by seven orbs. The entity seems to be pursuing the ship while murmuring "Av-o-lo-ha". However, much to Throckmartin's relief, storm clouds soon gather in the sky, extinguishing the moonlight as well as the entity.
"Dead! All Dead!": Down in his own cabin, Throckmartin explains to Goodwin that his party are all dead, victims of the glowing entity. He also shows Goodwin his chest, which is marked with a strange white ring. He begins relating his story beginning from many months ago: Interested in exploring the Pacific ruins of the Ponape islands, Throckmartin, his wife Edith, her Swedish assistant Thora and a fellow scientist named Stanton (possibly a relation of the Stanton in "The People of the Pit"?) persuade the superstitious natives to bring them to a small islet named Uschen-Tau, from which they can later study the nearby, forbidden islet of Nan-Tanach.
The Moon Rock: On the night of the full moon, the party hear chanting and a tinkling noise coming from Nan-Tanach.
Fantastic Novels May 1948, Virgil Finlay
Thora becomes stricken with a strange feeling of horror and rapture. The next day, the natives warn the outsiders to stay away from the foreboding isle. Nonetheless, Throckmartin and his party arrive at Nan-Tanach and eventually discover a stone door, which has a strange, electric, chilling effect when touched. When Thora sees the "moon door" she again relapses into a strange state.
Av-o-lo-ha: That night, the explorers try to monitor the door for motion, but a strange force makes them all fall asleep. The next morning, Thora is missing, apparently taken through the moon door.
Into the Moon Pool: Unable to breach the door by force, the remaining three wait for the next night to arrive, and situate themselves closer to door's location. The murmur of "Av-o-lo-ha" is heard, as well as the tinkling sound. While Edith succumbs to sleep, Throckmartin becomes somehow paralyzed.
Fantastic Novels May 1948, Virgil Finlay
Stanton however, rushes towards the door where he is then lifted up on a cloud of glowing mist. Infused with light, he is soon taken away by the mysterious force. The next night, Edith guards the entrance while Throckmartin tries to breach the door as soon as it opens, hoping to surprise the entity before it emerges. Inside, he discovers a strange pool upon which is concentrated rays of moon light. This apparently allows the "dweller" in the moon pool to manifest. As the entity surfaces, Throckmartin fires at it with a pistol, to no effect.
Amazing Stories May 1927, Frank R. Paul
A tentacle grabs him, but Throckmartin is able to somehow break free. Unfortunately Edith then rushes in, and the Dweller takes her instead.
Fantastic Novels May 1948, Virgil Finlay
Desperate and maddened, Throckmartin escapes out to sea in a daze. After he is rescued by a fishing boat, he then resolves to go back to Melbourne for reinforcements in order to mount a rescue. Thus, Throckmartin ends his tale to Goodwin.
The Dweller Comes: The next day on board the Southern Queen, Throckmartin tells Goodwin of his plans to have the moon pool explored by divers and the Dweller destroyed. However, in the evening, the storm clouds part and a clear full moon shines down once again upon the sea. Somewhat mesmerized, Throckmartin is driven to open his cabin door, after which the glowing entity captures him and takes him away. Back in the present (three years since Throckmartin's abduction just described), Goodwin now vows to go in search of Throckmartin's moon pool.
Famous Fantastic Mysteries Sept 1939

https://en.wikisource.org/wiki/The_Moon_Pool_(All_Story_Weekly,_1918)

"Conquest of the Moon Pool"

Famous Fantastic Mysteries Apr 1940, Virgil Finlay

The Dweller: While sailing to Ponape on the Suwarna, Goodwin and his crew spot a drifting vessel named the Brunhilda and find its Norwegian captain, Olaf Huldricksson (although Huldricksson's wife and daughter are missing). A little while later, the Suwarna comes across a wrecked hydroplane and welcomes aboard its sole occupant, the Irish-American, former British pilot Larry O'Keefe.
Larry O'Keefe:
Famous Fantastic Mysteries Nov 1939, Virgil Finlay
Olaf describes how a shining entity had abducted his wife and daughter and that he is intent on pursuing it. After Goodwin tells O'Keefe everything that had happened to him and Throckmartin three years ago, the pilot decides to join their expedition.
The Moon Door Opens—and Shuts: Goodwin, O'Keefe and Olaf make it to Nan-Matal and find the moon door. Using portable light condensers, Goodwin manages to amplify the partial moonlight to open the stone slab before the Dweller is expected to appear. However, an unknown figure from within attacks them. The door closes again and they all end up locked inside the stone chamber.
The Moon Pool: Within the moon door chamber, Olaf finds his daughter dead, and tries to revive her with the moon pool liquid, but is himself injured. The mysterious figure, a German named Von Hetzdorp, reports that the pool is radioactive and applies a cure to Olaf's paralyzed arm.
Famous Fantastic Mysteries Jan 1940, Virgil Finlay

As they explore the chamber, the image of a golden-eyed woman and a "frog-woman" appear on one wall.
"I'd Follow Her Through Hell!":
Fantastic Novels Sept 1948, Virgil Finlay
Uses gestures, the golden-eyed woman shows Larry how to trigger a hidden door, and then fades away. The quartet pass through the door and enter a travel car, which takes them deep into the bowels of the Earth, a cavernous area apparently left behind when the moon had been flung into orbit during the planet's early days. They soon arrive at an underground city.
Priestess of the Shining One: The quartet meet a green-clothed dwarf named Rador, who bring them in a corial (travel car) to Yolara, the "Afyo Maie" (leader) of Lora, capitol of Muria (the underground city).
Fantastic Novels Sept 1948, Virgil Finlay
Although Yolara shows interest in Larry, she horrifies the surface dwellers when she then disintegrates a rebel Murian citizen with a small cone-shaped weapon (a Keth).
The Angry, Whispering Globe: Back in their own quarters, Rador tells the humans of the "mayia ladala", the working class of Muria (one of whom had just been disintegrated). These lower classes are given to the Dweller of the moon pool (referred to as the Shining One) to "dance with". He also identifies the golden-eyed woman they had seen earlier as Lakla, a servant of the Silent Ones, and an enemy of Yolara. Before Rador can explain much more, an urgent summons from a shining globe commands Rador to leave the visitors.
Famous Fantastic Mysteries Dec 1939, Virgil Finlay
Larry and Goodwin soon drift off into sleep, but before he succumbs Goodwin sees a brief vision of Lakla hovering over Larry.
The Lovely Hand of Lurking Hate: In the following days, Larry continues to spend time with Yolara in order to try and gauge the power of her civilization. He learns that, besides the keth weapon, her warriors also have invisibility cloaks with which they can use to attack their victims unseen. At the same time, Rador shows Goodwin around the city. During his tours, Goodwin notes that the populace seem to be living in fear of the Shining One.
The Amphitheater of Hell:
Fantastic Novels Sept 1948, Virgil Finlay
In a grand ceremony, a group of ladala are given to the Shining One as a sacrifice ("to dance wth"). During the proceedings, Olaf tries to attack the creature, but Larry stops him before he is killed.
The Ladala are Awake: Larry and Goodwin retreat to their rooms, where Rador reports that the ladala have become roused by Larry and Olaf's display of resistance. Yolara soon calls Larry to her council room in order to "marry him", but Lakla and her frog warriors suddenly arrive, interrupting the ceremony.
"These the Silent Ones Summon!": Lakla tells Yolara that she has "three tal" (a week) to surrender the surface visitors to her masters the Silent Ones.
Amazing Stories June 1927, Frank R. Paul
When Yolara moves to attack Lakla, Lakla raises her yekta, a plant-like weapon. Eventually Lakla departs and Larry, Goodwin and Olaf are returned to their rooms. There, Olaf reports that Von Hetzdorp has convinced Yolara's second in command Lugur to help Germany conquer the world (and then make Lugur emperor). He also describes Lugur's demonstation of an anti-gravity bomb.
The Council's Decision: Rador learns that Yolara and her Council have agreed to join forces with Von Hetzdorp, and that they plan to kill Larry, Goodwin, and Olaf (as well as Lakla when she next returns). Ordered to bring the men to a temple for safekeeping, Rador instead turns their corial towards the outlands in order to escape the city. With Lugur and his men soon in hot pursuit, Rador leads them through a hidden passage through the rocks.
Dragon Worm and Moss Death:
Famous Fantastic Mysteries Feb 1940, Virgil Finlay
As Rador leads his friends towards the Crimson Sea, Lugur's men fall victim to a gigantic "dragon worm", as well as a field of paralyzing moss spores (which Rador had earlier managed to carefully avoid). Somehow, Lugur manages to hit Larry with a lucky shot, but Lakla and her Akka (frog warriors) soon appear and drive the Murian forces away.
The Three Silent Ones: Lakla and her Akka bring Goodwin, Olaf and the unconscious Larry to her realm beyond the Crimson Sea. After using a rainbow bridge to cross over a deep abyss, they soon enter the hall of the Silent Ones, avian-reptilian aliens who are able to revive Larry with their strange powers.
The Wooing of Lakla: While Lakla's Akka forces make plans to prepare for Yolara's attack, Larry and Lakla grow closer. Lakla also demonstrates her control over the deadly yekta plants.
In the Land of the Dweller:
Fantastic Novels Sept 1948, Virgil Finlay
Yolara and a group of her warriors sneak into Lakla's palace while hidden under invisibility cloaks. Fortunately, Lakla surprises her and her attack fails.
Famous Fantastic Mysteries Mar 1940, Virgil Finlay
As Rador and Olaf escort Yolara out of the city, Lakla shows Larry and Goodwin a crystal device which allows them to travel as astral projections. They journey to the cave of the Dweller and see that Throckmartin and his party are now soulless ghouls enslaved by the Dweller.
In the Beginning:
Fantastic Novels Sept 1948, Virgil Finlay
Afterwards, Lakla describes the origins of her underground realm. The Silent Ones are three members of the Taithu, an ancient race from the Earth's core, born from alien spores which had landed on Earth some time after the moon had flung itself into orbit. Deep inside this underground cavity, the Silent Ones then developed their mental powers and soon helped the Akka evolve from frogs into intelligent creatures. Eventually they decided to create life as well, and created the Shining One. The Shining One begins to go out of control and influences the other Taithu to create a religion on Earth's surface, based on worship of the sun and the moon. Eventually, as tectonic action changes the land above, the surface followers are driven down to Muria where they become the ladala. At the same time, the Dweller begins to emerge from a moon pool (built by its Taithu followers) in order to capture victims from the surface. Disturbed, the Taithu eventually leave the planet, but task the three Silent Ones to keep watch over their creation, the Shining One. Now, the Shining One is almost ready to consume the rest of the planet.
"The Keth Has Power": As the Akka army gathers, Lakla and her new allies consider how to counter Yolara's advanced weapons (the keth and the anti-gravity bombs).
Fantastic Novels Sept 1948, Virgil Finlay
Also, the Silent Ones tell Larry and Lakla that they must march into its embrace when it arrives. In this way, their love for each other will weaken the Shining One enough so that the Silent Ones can destroy it. Larry and Lakla agree to sacrifice their lives in this plan.
The Meeting of Titans: A massive battle ensues when the Murians arrive, but the Akka are victorious. Lugur tries to make a sneak attack but Olaf kills him (and dies in the process). When the Shining One approaches, Larry and Lakla go forth to meet it.
Amazing Stories July 1927, Frank R. Paul
When the Shining One recoils in some kind of instinctual fear, the Silent Ones attack it and send it (and Yolara) down into the abyss.
Von Hetzdorp Strikes!: With the Ladara having overthrown their oppressors in Muria, Larry, Lakla and Goodwin return to Lora to explore the Shining One's cave. Von Hetzdorp suddenly appears and attacks Goodwin, throwing them both into the nearby waterway. A strong current takes them out of the underground realm and ejects them on the surface. Von Hetzdorp drowns during this journey, but Goodwin survives. However, he soon discovers that the moon door of Uschen-Tau has been destroyed by an earthquake, thus sealing the path to the underworld forever.