R'lyeh
Ph'nglui mglw'nafh Cthulhu R'lyeh wgah'nagl fhtagn.
In his house at R'lyeh, dead Cthulhu waits dreaming.
R'lyeh is a nation of alien creatures who worshiped the Void. Their homeworld was destroyed in a great cataclysm and one of their homeworld's shards with the Great City of R'lyeh on it fell through the Sphere finally landing in an ocean. The impact destroyed the ancient empire of the Aboleths. The Starspawn of R'lyeh used their great mental power to enslave various native creatures of the seas. They wield armies of slave troopers, Starspawn warriors with Mind Blast and bizarre void creatures. The Starspawn are powerful Astral mages and the Starspawn priests can enter the Void Gate to summon void creatures that are Sacred to the people of R'lyeh. The coastal forts of R'lyeh generate half-human hybrids for free. R'lyeh starts the game underwater; however, with judicious use of amphibious troops they need not confine themselves to the sea.
It should be noted that while the Void Gate offers great power, using it is not without risk...
R'lyeh - Middle Age
The Great City of R'lyeh fell on an occean of a new planet. The Starspawn adapted and now they plan the conquest of this world. The armies of R'lyeh are filled with Deep One and Shambler slaves.
R'lyeh - Late Age - Dreamlands
Not much is known of this theme, but it seems that R'lyeh destroyed the previous civilizations of the seas. Now their Dominion drives people insane. Enemy commanders go insane and sometimes madmen leading other mad dreamers appears. Occasionaly even Void creatures emerge in their Dominion.
Reading Material
For background material and inspiration, see many of the tales authored by Howard Phillips Lovecraft. "The Call of Cthulhu" and "At the Mountains of Madness" are both good examples.
This author posits that an imprisoned or sleeping god would be extremely thematic, for those times before The Stars Are Right.
While a very modern mythos, compared to the systems inspiring some of the other nations, this has inspired not only other authors (such as August Derleth) but pencil-and-paper games, board games, a variety of odd merchandise, and even a musical titled 'Shoggoth on the Roof'.