I remember this story from about 1970. It probably was a comic, but there's a chance that it was an ilustrated novel. Style and aesthetics were similar to Conan the barbarian.
A warrior enters to a castle (or may be a tower). Inside there is a octopus-like monster who fights him. The monster can't bear noises and the warrior beats him hitting a gong, or may be a bell, that was by the gate.
I've googled for Conan, but I found nothing.