This cover falls into a category I call Monster Mash. A Monster Mash cover displays one or more creatures (often quite large) scaring the public, destroying private/public property, and/or engaging in an uncivilized romp and stomp with little or no motivation other than rampage itself.
Before "the Marvel Age of Comics" in which we were introduced to the likes of the Fantastic Four, the Avengers, et. al, Marvel specialized in comics featuring large destructive monsters (this particular comic is a reprint of those heady days). Keep in mind that the FF themselves faced a large monster (Mole Man's) in their first issue, and the Hulk and the Thing themselves were little removed from the category. Marvel was a bit tentative in their early superhero steps, not quite willing to abandon a modestly successful genre.
As to WMD #2, we see a typical large monster, with a typical nutty name ("Sporr" strikes fear into my heart). As such, it only rates a single scream.
But don't fear (or do...), it still ranks as a beloved cover. I mean look at those fearful citizens desparately shutting the door on a monster who is able to overgrow the whole castle! They are valiantly (if vainly) trying to stop "the thing that could not die" (I'm not sure how you prove that claim); and they waste precious moments on existential questioning when they should be running for it!
How can you not love it?