While well-read, there is no evidence that Robert Bloch was conversant in Atlantean.
The item at the left is a card from New Aeon edition the collectible card game "Mythos," published in 1997 by Chaosium. Bloch joins such Lovecraft protagonists as Charles Dexter Ward, Herbert West, Richard Upton Pickman, and Bloch's own doppleganger, Robert Blake, in battles against Lovecraftian horrors.