The Mystaran Solar System
by Håvard1st Planet (Mercury)
This planet is created as a result of the destruction of Damocles, so it doesn’t exist as long as Damocles is around. It is a scorched world, uninhabitable by most creatures. It has many gates to the Plane of Fire and Efreeti and other Fire Elementals make their home here. Red and Ruby Dragons also have many strongholds on this planet.
2nd Planet (Venus)
A misty planet not unlike Mystara, but with a higher temperature and a humid climate. The creatures who live here resemble those who dominated Mystara millennia ago. Dinosaurs still roam the forests and swamps of this world. Lizardmen, not unlike those found on Mystara may be encountered here. Millennia ago, the ancient Oltecs and Azcans discovered gates from Mystara leading to this world. Heldanners have their eyes on this world and may try to colonize it in the future. This world has no satellites.
3nd Planet (Mystara)
This is the world the Immortals pay most attention to in this Solar System, due to the great number of intelligent life forms and the powerful magic discovered among its inhabitants, among other things. It has two satellites, Matera and Patera.
4th Planet (Mars)
This is a desert-like planet. It is connected to the plane of Earth and many Earth Elemental creatures have found their way here. This is the home world of the Sandfolk, some of which were brought to Mystara during the Blackmoor Era. The Nithians colonized this planet during the height of their civilization and built huge structures here, including canals and Pyramids. A race of insect-men (Thri-Kreen?) is the dominant race. Brown dragons also have important strongholds on this world. It has two satellites. Thyatians have plans for colonizing this world, but these plans have been postponed.
5th Planet (Damocles)
This huge planet is home to an advanced civilization. The dominant race here is the Pyrithians, a green-skinned humanoid race which is believed to originate from another nearby Solar System (Epsilon Eridani). They are the ancestors of Mystara’s Emerondians. Damocles will be destroyed in the future, resulting in the formation of MMercury and MPluto. It has no satellites.
6th Planet (Jupiter)
This planet is an Air World, made up of breathable air. Its 63 satellites are actually floating continents home to various races. Many Air Elemental creatures live here. Some Alphatians stopped here on their way to Mystara and stayed. This has given belief to some that this is the original Alphatian Homeworld.
7th Planet (Saturn)
This planet is not unlike the 6th Planet, another Air World. This one is surrounded by a Ring of small asteroids, many of which are habitable. It has 27 floating continents. Fierce storms havoc this world. Blue Dragons have important strongholds here. Also, Faenare and many other flying races make their home on this world. Some Sky Gnomes have also established a colony here. They were part of a Serraine Space Program which Gnomes back on Mystara believe failed. Gold Dragons have a major stronghold on this world.
8th Planet (Uranus)
This is a water world. It has been settled by Alphatian Followers of Water. Sea Creatures of all kinds, including Sea Giants also live here. It has 13 satellites.
9th Planet (Neptune)
This is a water world. Many gates to the Elemental Plane of Water exist here and Water Elemental creatures make their home here. Sea Dragons have a major stronghold here. It has 13 satellites.
10th Planet (Pluto)
This is a new world, created by the destruction of Damocles. It is an ice world inhabited by various ice creatures and Frost Giants. White and Crystal Dragons have major strongholds here. When this planet is formed, Charon turns into this world’s satellite.
11th Planet (Charon)
This is a world of darkness. It is home to undead and other servants of Entropy. Night Dragons are believed to have a stronghold here.
These are old ideas of mine. Some are not unlike those Cab posted. I'm not saying the differences between mine and his mean mine are better, but I wanted to post my old ideas before making comparisons.
The 2nd, 3rd and 4th worlds are hollow as are many of the various satellites.