Has anyone usedhttp://en.wikipedia.org/wiki/T%C3%A9kumel
The world of Tékumel, Nu Ophiuchi d (a.k.a. Sinistra d), was first settled by humans exploring the galaxy about 60,000 years in the future, along with several other alien species. Their extensive terraforming of the inhospitable environment, including changing the planet's orbit and rotation rate to create a 365.25-day year, disrupted local ecologies and banished most of the local flora and fauna (including some intelligent species) to small reservations in the corners of their own world, resulting in a golden age of technology and prosperity for humankind and its allies. Tékumel became a resort world, where the wealthy from a thousand other stars could while away their time next to its warm seas.
Suddenly, and for reasons unknown, Tékumel and its star system (Tékumel's two moons, Gayél and Káshi, its sun, Tuléng, and four other planets, Ülétl, Riruchél, Shíchel, and Zirúna) was cast out of our reality into a "pocket dimension" (known as a béthorm in Tsolyáni), in which there were no other star systems. One hypothesis is that this isolation happened through hostile action on the part of an unknown party or group. Another is that the cosmic cataclysm was due to over-use of a faster than light drive which warped the fabric of space. No one knows, but the inhabitants of Tékumel, both human, native, and representatives of the other starfaring races, were now isolated and alone.http://en.wikipedia.org/wiki/Needle_(module
In Needle, the player characters are dispatched to a far jungle to retrieve a magical obelisk. The characters return to their employers with the obelisk after a perilous journey, and find out that the obelisk is a portal to another world, which the characters must pass through and learn how to deal with the residents on the other side.
In this adventure, the player characters volunteer for a king to explore a dense jungle that was once home to a great civilization, with a magic obelisk at its center. In Part 1, Ruins of Empire, the party travels to the jungle and explores the ruins. In Part 2, Retrieval, the party leads a team hampered by disease and jungle animals to transport the obelisk to the king. In Part 3, The Powers That Be, assuming the party is successful, the obelisk is placed in its new position, where it reveals a gate to another world.
Tekumel has a similar back-story to Lythia, and Needle has a million tonne Godstone.