As I'm getting ready to run a Pathfinder game pretty soon that will at least start on a homebrew prime called Vidalok, I figured I'd drop a post about the prime here incase anyone else is interested to use it in their own games, or has suggestions on how to develop it/make it better! I've always felt that little random primes are a pretty great thing to have.
The basic idea of the Vidalok prime is that, during its ancient history (an unknown time ago) there were a many two-way portals between it and the Quasi-Elemental Plane of Lightning. Some lightning creatures came through, conquered territory, founded vast civilizations, subjugated the native humans, etc etc etc. Eventually, for a presently-undefined reason they left the prime, and their numerous lines of Lightning Genasi descendants naturally inherited the nobility and ruling casts. The most popular and well-known powers on the prime are, consequently, all powers of Lightning, Storms, Weather, etc.
The most prominent races on the prime are Humans, Dwarves, Lighting Genasi, Air Genasi, Desert Elves, Half-Elves, Half-Giants (Storm Giant), and Avariel.
The Half-Elves are outcasts and quite uncommon, as they are in many settings. The Avariel are somewhat backward and uncivilized, with no settlements on the the 'main continent', instead being the mysterious barbarians from the frigid north. The desert elves primarily worship Set, the and the only dwarven god represented on the prime is actually Dugmaren Brightmantle, so Vidalok's dwarves are somewhat scholarly and inventive (the role often assigned to gnomes).
The Lightning Genasi, as mentioned previous, are the nobility. There are many Lightning Genasi families, and they rarely marry humans, preferring to keep to their own race/social standing. Air Genasi are much less common than the Lightning Genasi, and while they are still nobility they are commonly considered by the people of Vidalok to be "what happens when a Lightning Genasi dilutes their blood by marrying a commoner." Thus, they are socially viewed as being less pure, or inferior, Lightning Genasi.
Sorcerers in the setting are most frequent among the Genasi, and (regardless of race) typically find their talents leaning toward lightning and air-elemental magic. Wizard organizations, similarly, favor the teaching and learning of lightning magic.
The technology level of the prime is slightly higher than that of a typical prime (though not as advanced as Iron Kingdoms, probably nearer to Eberron-level) because of a magical process, discovered by the Dwarves, which 'harnesses' lightning, thus making storms into a source of fuel for basic inventions.
The people of Vidalok also prize diviners, perhaps even higher than elemental casters. They have a strong traditional belief in "cloud astrology," where the state of the sky is supposed to determine the future of children born under it, in addition to divinations based around the positions of Vidalok's 16 moons. Most nobles have at least one diviner in their employ to advise them. There are several known islands off the various coasts of the main landmass of the setting, but sea travel is only attempted when a diviner has predicted a smooth trip. The "right of passage" when children become adults, additionally, is when they receive their first divination. For the poorest families, this fortune is often the only one they will receive, and those in rural communities will often have all the children of the same age make the commute together to the nearest seer to the village in the early spring to receive their divinations together.
Sssso, yes. As you can see, I have a fair bit of stuff defined, but I also have a lot of stuff that I haven't yet decided on (mainly the recent history). All of my Vidalok information is available online at http://eroding.net/lin/ if you wanted to see more (eg. I drew a map). Note that some of the stuff in the races section is sliiiightly made up? Especially the genasi, there was fudging around with those. I don't know if Pathfinder Genasi have been released yet or not ._. The made up stuff isn't really final.
I also may take Stronmaus out of the deity roster, because my ex will not stop threatening to make a character with like 6 WIS and INT who worships "The Strong Mouse." Grr, strong mouse.