Ditko had drawn three stories for the series early in his career. The series continued until #50 in 1961, with several long publication gaps along the way. I'm almost certain this particular story was drawn well before its publication, but also does not date from the 1953 era of Ditko's previous BLACK MAGIC stories. From the style I think I'd place it around 1957, which might be a clue to its origin, but I'd be curious what other people think.
Anyway, "The Black Fog" is a story about a man who is plagued by dreams of darkness, death and falling. He gets a pill from his friend that's supposed to keep him awake for 24 hours to stop the dreams, and if that sounds like a bad prescription to you, well, there's a good reason for that.
Whatever the story behind the story, it's a well drawn effort from Ditko, who does a good job with the nightmare sequences, with the smokey blackness enveloping the character and the robed figure of Death. There are a few stray panels that seem off, maybe re-drawn by someone else during whatever path saw this story published when it was, but that's a minor thing compared to the strengths of the story.