[Cthulhu Mythos + no system, but there is a mental link with the partner + male protagonist's perspective + no clear emotional line, pure friendship from birth to death]
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Do you want some 1920s Cthulhu flavor?
There are weird exotic landscapes and mysterious death cults.
An intricate chain of clues, a loyal and vicious partner.
There is also a salvation organization, black technology, and magical powers.
And a chief criminal who committed suicide out of fear of crime.
