Setting -
Agartha. It is a name shrouded in mystery. At least by outsiders. For them, it fades from the mind before the thought can direct a pen to scribe it. The whisper of it fades on the winds before the sound reaches the ear of the listener. It is a place of legend, where dead empires breathe yet again. From the earliest days of this world, when the Ice Gods first traced their fingers upon the scorched landscape of the Fire Gods to the present, and at every point in between, this realm grows. The Elder Gods set down the law to the Younger; Keep the knowledge of this place secret. With few exceptions, so has it been.
Still, legends whisper of two worlds; one known to the inhabitants of the outer world and the other as the hidden world, Agartha. Some even speculate that Argatha is home to the Azlanti that left Golarion so long ago. Only the Agarthans know for certain. Their hidden world lies deep within the earth, deeper than even the caverns of the Underdark, safe from the mining of the dwarves and the turmoils of the outer world. It stays hidden because it has the power to do so, a reflection in a mirror unable to be touched. A power its inhabitants protect as jealously as a dwarf protects his mines. It lies in ancient magic and in technology too complex to be understood by most. Shut off from the outer world, Agartha is only accessible through a limited number of portals, warded from magic and indestructible to physical assault. These barriers are mirrored on the various planes, so even beings strong enough to travel in those realms find themselves unable to cross.
Shangri-La is the capital city of this world, the nexus of a series of connected cities, connected empires, each self sustained and varying in their appearance. Shangri-La is home to the intellectuals; mages of immense power, clerics of alien gods, mystics and and psionics of no compare. The Council of Five meet to discuss matters of state, but rarely intrude on the sovereignty of the satellite empires. Each of the council members would rather spend their time in contemplation than in matters mundane. Unlike the drow these people, the Agarthans have risen above gathering or using their power for selfish reasons. Well, most of them have. Even in a paradise there are those that stand apart from their brothers. Acknowledging this fact there are whispers of a Sixth Member of the Council.
As on the surface the world a mirror of a sun lights Agartha, motionless but waxing and waning in its brightness. It is a crystal of immense size, placed in the mile high roof of this underground world, and its light is not diminished over distance. Though a mere shadow of its partner above, it radiates enough heat to destroy anyone foolish enough to get too close.
In some ways Agartha is a land of the lost, providing sanctuary to beings and creatures long extinct on the surface. In other ways, the Hidden World far surpasses its cousins. It is here that the Antlanteans might mingle with the Titans, while gazing upon the construction prowess of the Mayans or Egyptians and sipping tea from the First Empire of the East. It is here that the Children of the Ice Gods might swim in waters warmed by the breath of the elemental races. Magic and Technology co-exist and overlap. All is possible in a world such as this. While the dwarves and men of the outer world may occasionally dream of this place as a paradise, and the rare drow priestess may dream of conquering it, this is not a world of innocents. It is a world of power and danger, held in check by a careful balancing of power. Here anything is possible. Here anything becomes probable.