It's in this issue--Conan the Barbarian #3 (February 1971)--that Marvel Comics' Conan became the "real" Conan.
The first two issues in the series--written.by Roy Thomas and drawn by Barry Smith--were both perfectly good sword-and-sorcery tales. But neither of them had that Robert E. Howard vibe to them. Conan was there. Smith drew him effectively and Thomas did a good job of catching his personality. But something really didn't quite seem right. I think it's the plots. One involved a wizard who was peering into the future. This includes allowing us to see some of his visions, which includes the sight of a NASA space ship in orbit--which is simply a bad fit for a Conan story. The second issue involves a small, hidden civilization of intelligent apes, which seemed to belong more in an Edgar Rice Burroughs universe than in the Hyborian Age.
(Roy Thomas makes these points about the first two issues himself in the afterward to Dark Horse's trade paperback reprints of the early issues, so I'm stealing from the author here.)
The 4th issue of the series would be an excellent adaptation of "The Tower of the Elephant," one of the original Conan tales. But I would argue that the 3rd issue is when the book really hit the right tone. This issue, by the way, was apparently written and drawn after "The Tower of the Elephant," but published first because Thomas realized it fit better there in terms of internal chronology.
Barry Smith does a wonderful job bringing a lyric beauty (a phrase I am also stealing from Thomas' afterward) to the idea of a dying god. Names and settings are changed to fit the concept into the Hyborian Age. The story is streamlined a bit and one can argue even improved upon. The prose story (unpublished in Howard's lifetime) is largely excellent, but Howard gets a little too carried away in name-dropping historical figures who really fought at Clontarf and this throws off the pacing.
So this time, it's Conan who meets the God Borri and then ends up fighting against the Hyperboreans--who are the people that worship Borri. Other plot elements include a femme fatale who is playing a king and a soldier against one another; another soldier who befriends Conan but who is prophesied to die by his girlfriend; and Conan's drive to find and kill a particular Hyperborean who had tortured him.
The scenes with Borri bookend the main events of the story. The dying god does not seem to directly effect events, but give the entire story a sense of finality and perhaps a small sense of futility regarding the wasted efforts and small-minded goals of us short-lived humans. But whatever moral we take from the tale, Barry Smith's art makes it look awesome. And, for the first time, the Conan of Marvel Comics was really believable as Conan.