I bring this up because this is precisely what happened in the case of "Witch of the Demon Seas," which first appeared in the January 1951 issue of Planet Stories. Though credited to "A.A. Craig," the yarn is actually the handiwork of Poul Anderson, another of whose stories is featured in the same issue under his usual byline. Like many pulp fictioneers, Anderson had an incredible work ethic: sixteen of his short stories and novellas were published the same year as "Witch of the Demon Seas." It's difficult not to feel inadequate when faced with such a remarkable output.
Though nowadays Anderson is most remembered for his science fiction, notably his tales of Nicholas Van Rijn, David Falkayn, and, of course, Dominic Flandry, he was also an accomplished writer of fantasy. Three Hearts and Three Lions is perhaps the best known of his fantasies, at least for players of roleplaying games, but The Broken Sword is, in my opinion, equally worthy of admiration (both appear in Gary Gygax's Appendix N, for what it's worth). Pulp writers had to be omnivorous if they wanted to make a living at writing, hence the existence of stories, such as this one, that might broadly be described as "fantasy" (or perhaps sword-and-planet, which was the bread and butter of Planet Stories during its 71-issue run).
Regardless, "Witch of the Demon Seas" certainly takes place on another world, one whose surface is almost entirely covered by water. What civilization exists can be found on numerous island kingdoms, such as the Thalassocracy of Achaera, whose ruler is Khroman the Conqueror. Khroman is "a huge man, his hair and square-cut beard jet-black despite middle age, the strength of his warlike youth still in his powerful limbs." He's also honorable, which we learn early in the story, when he tells his advisor, Shorzon the Sorcerer, that he intends to treat his recently defeated enemy, the fair-haired pirate Corun, with respect, as he is "the bravest enemy Achaera ever had."
When Khroman interrogates him, Corun reveals much about his origins and the reasons for his turn to piracy. Come to think of it, the interrogation reveals a fair bit about Khroman as well.
Khroman stared at him in puzzlement. "But why did you ever do it?" he asked finally. "With your strength and skill and cunning, you could have gone far in Achaera. We take mercenaries from conquered provinces, you know. You could have gotten Achaeran citizenship in time."
"I was a prince of Conahur," said Corun slowly. "I saw my land invaded and my folk taken off as slaves. I saw my brothers hacked down at the battle of Lyrr, my sister taken as concubine by your admiral, my father hanged, my mother burned alive when they fired the old castle. They offered me amnesty because I was young and they wanted a figurehead. So I swore an oath of fealty to Achaera, and broke it the first chance I got. It was the only oath I ever broke, and still I am proud of it. I sailed with pirates until I was big enough to master my own ships. That is enough of an answer."
"It may be," said Khroman slowly. "You realize, of course, that the conquest of Conahur took place before I came to the throne? And that I certainly couldn't negate it, in view of the Thalassocrat's duty to his own country, and had to punish its incessant rebelliousness?"
"I don't hold anything against you yourself, Khroman," said Corun with a tired smile. "But I'd give my soul to the nether fires for the chance to pull your damned palace down around your ears!"
"I'm sorry it has to end this way," said the king. "You were a brave man. I'd like to drain many beakers of wine with you on the other side of death." He signed to the guards. "Take him away."
Upon hearing this, Shorzon takes an interest in Corun, for reasons that soon become clear. Together with his daughter, Chryseis, the story's titular witch, he visits the pirate in his solitary cell. The sorcerer then offers him "life, freedom—and the liberation of Conahur!" Naturally, Corun doubts the wizard's sincerity, but Chryseis, a remarkable beauty, reassures him, "You can help us with a project so immeasurably greater than your petty quarrels that anything you can ask in return will be as nothing. And you are the one man who can do so."
"What do you want?"
"Your help in a desperate venture," said Chryseis. "I tell you frankly that we may well all die in it. But at least you will die as a free man—and if we succeed, all the world may be ours."
"What is it?" he asked hoarsely.
"I cannot tell you everything now," said Shorzon. "But the story has long been current that you once sailed to the lairs of the Xanthi, the Sea Demons, and returned alive. Is it true?"
"Aye." Corun stiffened, with sudden alarm trembling in his nerves. "Aye, by great good luck I came back. But they are not a race for humans to traffic with."
"I think the powers I can summon will match theirs," said Shorzon. "We want you to guide us to their dwellings and teach us the language on the way, as well as whatever else you know about them. When we return, you may go where you choose. And if we get their help, we will be able to set Conahur free soon afterward."
Corun shook his head. "It's nothing good that you plan," he said slowly. "No one would approach the Xanthi for any good purpose."
"You did, didn't you?" chuckled the wizard dryly. "If you want the truth, we are after their help in seizing the government of Achaera, as well as certain knowledge they have."
"If you succeeded," argued Corun stubbornly, "why should you then let Conahur go?"
"Because power over Achaera is only a step to something too far beyond the petty goals of empire for you to imagine," said Shorzon bleakly. "You must decide now, man. If you refuse, you die."
This is the proverbial offer that one cannot refuse, so, with some trepidation, Corun agrees. Shorzon and Chryseis then lead him to a fully-crewed vessel that will take them to the Xanthi, a race of inimical fish-men with a history of warring against the other peoples of the world. The ship leaves Achaera – without the knowledge of Khroman, I might add! – on a quest whose ultimate objective, Corun suspects, is far from virtuous. For the moment, though, he does not care, as he only wishes "to live! To die, if he must, under the sky!"
"Witch of the Demon Sea" is a delightful romp, filled with monsters, magic, sorcery, and swordplay. The characters, starting with Corun himself, are somewhat archetypal, let us say, but Anderson tells the story with such energy and enthusiasm that I soon didn't care. The story is interesting, too, because it contains elements that could be described as "secret sci-fi," thereby further muddying the waters regarding how to classify this yarn. For myself, I prefer to classify it as "fun" and leave it at that.