Any world created by Gygax will have a planet name ending in -rth, with two vowels before. Oerth, Aerth, Eurth, Eirth, Airth, Eerth, Oarth, etc. are all perfectly valid Gygaxian world names.
Funny thing is, in its French version of Greyhawk (setting name is unchanged, but the city becomes Faucongris), Oerth is named Taerre (since Terre=Earth). I expect the German version to be something like Orde (Erde=Earth).
Trivia: The Forgotten Realms' world was named Toril, copying Jeff Grubb's homebrew's name. But Toril starts with a T, which means it wasn't at the top of the index. So, Abeir was tacked on before, just so that Abeir-Toril would be the first entry in the index.
My homebrew's solar system works like this:
Prime is the name of the sun. It's what people can expect for such a thing: a mind-boggingly big sphere of fire, heat, light, and raw energy.
Limiole is the first planet. A hot place, rich in metals and crystals, with intense telluric activity. It's the homeworld of azers and genies. All life here is either supernatural, in order to resist to the intense heat and bright, or very primitive -- vermins and oozes. Its color in the night sky is bright gold.
Parele is Limiole's moon. Its orbit, which doesn't bother itself with real-world astrophysics, put it constantly in the shadow of its "mother-planet," shielding it from Prime's fiery rays. As a result, Parele is a white world of ice and snow. It's as bright and dazzling as Limiole, but cold. The exiled genies known as Qorrash lives there, and it is very possible their magic could explain Parele's quirky orbit.
Peline is the second planet. Inhabited by fey, animals and magical beasts, Peline is a beautiful, if wild and harsh, world, that seems perpetually in autumn. With the exception of a couple tiny seas and a few mountaintops, the whole landmass is covered by forests. Peline is a russet world.
Peline has no moon but it has a ring
Lourane, that orbits it lowly enough to be within its atmosphere. Lourane is the home of mighty elemental nobles, as well as genie outcasts from Limiole or the most powerful and excentric amongst Peline's inhabitants.
Edhel is the third planet. Unless the third planet is
Rhane. Together they are called
Erdelane and forgotten legends tell in the past, it was a single planet. Now it's two twin planets of the same size. Edhel is inhabited by just about everything, as it is the campaign world. Rhane is inhabited by the gods from the people of the surface, and by petitioners and servants of the gods.
Edhel's core is missing. Instead, the hollowness in its heart, that resulted from its separation with its twin, has been filled by an infection of fiends, like worms within an apple. This fiendish cancer is made up of three parts. The uppermost is the
Cataract, an inverted world where the ground is a ceiling and there is no bottom. There, daemons live. Buidings hang or dangle from the ceiling rock, tunnels and caves are dug within said ceiling, weakening it. Sometimes, huge chunk of rocks break off, falling into the void, bringing daemons, buildings, monsters, visitors, and whatnot into the
Abysm, a foggy haze pulsating with malevolent, nauseating light. Demons live within that haze, teleporting or jumping from rock to rock, wrecking havoc. Theirs is a world of endlessly falling, tumbling, colliding meteors. There they destroy and kill things, and when nothing's left to destroy or kill, they create monstruosities for the sole purpose of destroying them. Sometimes, they are destroyed instead. But even infinities have an end, and at the end of the fall, the rocks conglomerate into
Hell, where devils are using all those material to build a new planet. One day, maybe, Edhel will implode, its surface inhabitants plumetting to their hellish doom through the Abysmal fog, and a new fiendish world will be born. Everytime the daemons trick one more soul into evil, one more rock fall from the Cataract into the Abysm. For the fiendish core is nothing but the physical symptom of a spiritual disease.
Duedrac, the fourth planet, is an enigmatic world. Constantly surrounded by thick, impenetrable green clouds, nobody ever came back from it. [Fact is, said green clouds negate all magic. It's not easy to leave a world if you can't use
planeshift,
teleport, or even
fly.] Duedrac is thus associated to its moon,
Meravone, home of formians, fungi, and various other insectile or quasi-vegetal lifeforms.
Lerebre, the fifth and last planet, is a grim place indeed. Too far from Prime to get enough heat and light, it is a dark and cold place. The weather is harsh, full of storms, and lightning is for most lifeforms the only sufficient source of energy. The vegetation there use metallic spines so as to better gather the precious electrical energy, just like vegetation on other worlds use chlorophylian leaves so as to better "harvest" sunlight. It's a world where the undead, unhampered by the lack of light and of heat, proliferate. The native world of a strange, faceless folk (the Changeling from MM3) ruled by enigmatic and cruel monsters (Encephalon Gorger from TOH2) is deadlocked in a constant war between the living and the dead.
Its two moons,
Apobre and
Obrodon, are even worse. These two small worlds are desolate wastelands. Temperature is higher than on Lerebre thanks to intense volcanic activity, but this doesn't improve the landscape. The birthplaces of kytons and night hags, who turned these two moons into giant charnel houses to fuel their necromantic experiments. Demodand arose from one of them, and they are in turn the progenitors of all other fiends. Now their servants steal corpses from other planets (and especially the nearby Lerebre) in order to keep their labs well stocked. They're partly responsable for the undead invasion of Lerebre -- and don't give a damn, of course.
