Although Kaelaross is just one world, its connections to other planes of existence have had profound effects on its history, especially in the last 50 or so years.
Kaelaross itself is on the Material Plane, which includes all sorts of other worlds but basically share the same rules of reality. Getting to and from these other worlds on the Material Plane is possible, but would require either magic spells or else ships that could fly beyond the clouds and into the space between worlds. Although a marvellous concept, this is somewhat beyond the scope of this description.
The Ethereal Plane is what links the other planes of existence together - it surrounds and borders all the other planes including the Material Plane, and nearly all travel from one plane to another will involve passing through the Ethereal Plane. The Ethereal plane is a relatively safe but boring place, with very few inhabitants, but also few dangers. The Ethereal Plane has been described as a place of silvery grey clouds without gravity or sunlight where travellers float as if suspended in water but without dampness or drowning. Those people who have travelled the Ethereal Plane say that their need for sleep, food and water is greatly diminished, and there is one account (though perhaps unreliable) of a wizard who spent 120 years in the Ethereal Plane and only aged a year or so. Some monsters on the Material Plane can not only sense creatures close by in the Ethereal Plane, they can use their deadly abilities against ethereal creatures. Medusae, basilisks and cockatrices are among these trans-planar threats.
The Elemental Planes of Earth, Air, Fire and Water are all hostile to normal life, but often include their own sorts of inhabitants. The Elementals that wizards and magic items can summon make their home here, and others such as Fire and Frost salamanders, djinn and efreet are also found.
The Elemental Plane of Earth is nearly solid stone and earth, with only a few pockets of air, water and lava found. Finding an air (or maybe water) pocket is essential if a human visitor is to avoid being crushed and suffocated. However, if a pocket of air can be found, the plane is tolerable in temperature and not many dangerous inhabitants. A few valuable minerals can also be picked out by those with skill in prospecting and mining.
The Elemental Plane of Water is like a vast, dimly lit ocean without a surface. There are pockets of air and earth (but no fire pockets). Any visitor who can cope with breathing underwater should be able to stay on this plane for a while. Creatures of seas and oceans of the Material Plane are occasionally encountered here, adding weight to sages' theories of gates between the Elemental Plane of Water and deep abysses in the oceans of Kaelaross.
The Elemental Plane of Fire has two major problems - firstly the intolerable temperature will kill any mortal creature without some sort of protection. Anyone travelling to this plane must be able to tolerate hot flames, or their death will be a quick one, with cremation rather than burial. Secondly the Plane of Fire is home to some quite dangerous and volatile creatures - Fire salamanders and efreet. Being able to either negotiate or else fight off these creatures is necessary for any extended stay where encounters are inevitable. There are some pockets of clear air, while lumps of rock from the plane of earth either melt into pools of lava or else glow like burning coals.
The Elemental Plane of Air is in many ways the safest of the elemental planes. The biggest problem is the electrical storms. This plane has no gravity, so everything - clouds, natives and visitors, float around. There are occasional spheres of earth and fire that float around. Any water here tends to evaporate and turn into clouds within a matter of hours, and visitors are recommended to bring water as they are likely to get thirsty. The djinn are found here, but they can be tempermental and fickle in dealing with those who intrude on their domain.
The Planes of Law and Chaos are the respective homes of archons and demons. With both sets, there is a progression of planes that get further and further from the Material Plane.
The Planes of Law closest to the Material Plane seem like material worlds, but more ordered and peaceful. As a planar traveler moves further up through the planes, they become less like the material plane and more
structured and abstract. Whereas the first plane of Law, Halloris, seems to be a pleasant countryside where crops grow healthily and there are fewer predators and bandits, explorers who have visited Iconnos, the 34th Plane of Law report it to be full of straight edges, flat surfaces and regular geometric shapes. Only one person has been to the 50th Plane of Law and returned to describe it - apparently it is full of different shining lights, each at a carefully set, finely tuned brightness. The lights themselves were arranged into exact patterns and the explorer felt that his very presence was upsetting the symmetry and harmony of the plane. The poor chap never quite regained his sanity and went blind after returning to the material plane due to his desire to stare at the sun.