Cover of TV Century 21 (20th July, 1966) featuring The Hood from Thunderbirds

a) Perhaps Moebius used this magazine cover as reference material for his Baron Harkonnen illustration for Jodorowsky's unmade Dune in 1975.

See: Referenced in illustration of Baron Harkonnen for Jodorowsky's Dune (1975) by Moebius? 

b) Perhaps Giger who was involved in the Dune project and got to know about the other people working on it  andsaw what Moebius was doing with the Baron Harkonnen illustration , resulting in him wanted to do something with it in Mordor V.

See: Referenced in Mordor V (1975) by HR Giger?

c.) Perhaps later Jack Kirby found out what sources of reference Giger and decided to use it in his illustrations for The Eternals #8 (1977)

See: Illustration of the undersea Deviant City ruins for The Eternals #8 (1977) by Jack Kirby? (to come)