This Rogue Planet is without a star, and instead orbits as a White hole, which keeps it warm and always day time. It is considered the most horrific of all the planets within the Polaris Galaxy, with it's natives being Elaagloth, who live within ruined cities which are symbols of a once great civilization driven to insanity or slavery, raised now only as food for the Elaagoth.
The average tempature upon R'yleh is around 75 degrees C, meaning very few beings can survive upon it's surface. However, this also means that many elements have traveled closer to the surface, making the atmosphere 50% Oxygen, and 20% Co2, with the other 20% being Noble Gases, like helium or Xeon.
Ash, the king of Polaris and Solaris, and who thinks himself a protector/ruler of the galaxy, has made the capture or destruction of this planet among his top priorities.