Most of the gods in the Hyborian Age stories have a clear historical or literary source, but I'm not aware of any source for a god who wants no worship & grants no boon, aside from the will to persevere in the face of adversity.
"They have no hope here or hereafter," answered Conan. "Their gods are Crom and his dark race, who rule over a sunless place of everlasting mist, which is the world of the dead. Mitra! The ways of the Aesir were more to my liking."
"What of your own gods? I have never heard you call on them."
"Their chief is Crom. He dwells on a great mountain. What use to call on him? Little he cares if men live or die. Better to be silent than to call his attention to you; he will send you dooms, not fortune! He is grim and loveless, but at birth he breathes power to strive and slay into a man's soul. What else shall men ask of the gods?"
His gods were simple and understandable; Crom was their chief, and he lived on a great mountain, whence he sent forth dooms and death. It was useless to call on Crom, because he was a gloomy, savage god, and he hated weaklings. But he gave a man courage at birth, and the will and might to kill his enemies, which, in the Cimmerian's mind, was all any god should be expected to do.
"Such is not the custom of my people," Conan growled, "nor of Natala's either. The Hyborians do not sacrifice humans to their god, Mitra, and as for my people—by Crom, I'd like to see a priest try to drag a Cimmerian to the altar! There'd be blood spilt, but not as the priest intended."
Crom, the name of the god of the Cimmerians in Robert E. Howard's Hyborian Age adventures of Conan the Barbarian, is invoked or named in nearly every episode, but very little is said about him. Robert E. Howard does not expand on this explicitly in any of his letters, but it's worth noting out that before Conan the Cimmerian called on Crom, Conan the Reaver did:
I had clambered the cliffs—no, by the thunder of Crom, I was still in the cavern! I reached for my sword—
"Conan" is a traditional Gaelic name (cf. Arthur Conan Doyle, Conan O'Brien, etc.), and Howard identified to Lovecraft and others as Irish-American, with a love of Irish history and language (as far as he could, in rural Texas.) Before he created the Hyborian Age, he created the character of Conan the Reaver in "The People in the Dark" - an explicitly Irish raider:
Then suddenly I remembered and laughed to think that a fall on his head should render me, Conan of the reavers, so completely daft. Aye, it all came back to me now. It had been a raid on the Britons, on whose coasts we continually swooped with torch and sword, from the island called Eireann. That day we of the black-haired Gael had swept suddenly down on a coastal village in our long, low ships and in the hurricane of battle which followed, the Britons had at last given up the stubborn contest and retreated, warriors, women and bairns, into the deep shadows of the oak forests, whither we seldom dared follow.
The implication is thus that the Cimmerian god Crom was inspired by the old Irish god Crom Cruach, much as the Celts themselves in Howard's pseudo-mythology were descended from the Cimmerians. The Hyborian Crom is not exactly like his Irish inspiration - notably, accounts of Crom Cruach speak of infant sacrifice as a kind of blood libel, while Robert E. Howard's Cimmerians wouldn't put up with that kind of thing.