Forbidden Worlds was a fantasy comic published by the American Comics Group, which ran for 145 issues between 1951 to 1967. It changed its title to Young Heroes after pressure from the 1954 Senate subcommittee hearings on the dangers of comic books, but soon reverted.
Adventures Into the Unknown was one of the first ongoing horror comics title. Also published by the American Comics Group, it ran for 174 issues between 1948 and Aug. 1967. It also survived the Senate Subcommittee on Juvenile Delinquency hearings.
Dark Horse Comics previously registered a comic book trademark for Seduction Of The Innocent, the book that provided the backbone for those Senate hearings.
In the past week, Dark Horse has also registered trademarks for both Adventures Into The Unknown! and Forbidden Worlds.
It has been publishing archive editions of both series over several years. But they have competition by Roy Thomas and his UK publishing company PS Publishing who appear to be reprinting the same material.
Could this be the reason for the trademark registration?