I was actually looking at some of the terrific horror covers that Neal Adams drew for the Distinguished Competition, when I came across these early 70s Marvel Monster covers.
Tomb of Dracula #1 launched the King of the Vampires in his own color comic in 1972. Entirely spooky and would entice you to buy the comic, especially if you were a fan of Hammer horror films.
Adventure into Fear #11 was Man-Thing's second appearance in the title, also in 1972. This cover plays on a recurring theme by Adams: children playing innocently while a monster approaches them from behind. In this case, it's the monster (Man-Thing) that is innocent, as the kids draw a Satanic pentagram in the dirt.
Marvel Spotlight #2 was the first appearance of Jack Russell, Werewolf by Night. But this has to be one of the worst covers that Neal Adams has ever produced. A series of panels showing the Werewolf changing, and he doesn't resemble the version drawn by Mike Ploog at all. What the heck, I had to buy this comic anyway! Nuff Said!
Update: Comments from my old MT blog...