According to Wikipedia "Challenge of the Unknown 6" was used as example of violent and gruesome imagery in the 1950s U.S Congressional Inquiries into the influence of comic books on Juvenile Delinquency that led to the Comics Code Authority. Here's "Villa Of The Vampire" from "Challenge Of The Unknown 6" and after the Eerie Publications rework "The Vampire Lives". It also looks like DC
"reworked" the title of this
book a bit for one of their classic
Silver Age Superhero Teams.