Ashworld is a collaborative setting created (and being created) by the folks at the Bay 12 Forums.
In a world inside a hollow sphere, volcanoes form islands amidst a sea of their ash, where the souls of the dead swim. In the center of the world is the sun; as there is no day or night, time is measured through other means, such as the Tides, which rise and fall over a period analogous to a year.
Can be found here.
Ashworld provides examples of:
- Hollow World: The sun's in the center, gravity points outwards, and so on. However, there's no opposite world on the other side of the shell, only oblivion.
- Hungry Jungle: Literally. The trees are conscious (Genius Loci) and carnivorous. They will eat you. Unless you're a maggot man, in which case you're inedible and will be left alone.
- The Tower: An obsidian tower reaches all the way from the ground to the sun. It appears in numerous myths, notably about the end of the world. Every 200 tides (years), it emits a magical pulse creating new magic gems and temporarily improving said gems' power. Every 3800 years the pulse makes the tower crack violently, and people believe it will one day shatter from that, leading to the end of the world. Dwarves also climb it every 50 years. None survive the attempt, but are believed to reach some sort of heaven.
- World Tree: All the (carnivorous) trees are tied to the Gretree, which is a great tree growing somewhere in the world. Giant ashsea creatures dwell within its roots. It is so great that it goes all the way up from the seafloor to the surface of the ashsea.