The Rillario Archipelago is a world of islands, from the central ones that can be over two thousand miles across, where the central goverments are located, to tiny ones that only stick out of the sea at low tide.The magic and religions of the inhabitants of those varied lands are bound up with the elements and their elemential overlords.
Only the greatest wizards and witches have any idea of what goes on in the elemential planes, but what they know, from the handful who went there and returned alive, is this. Even for elementials, the planes are a dangerous place. Elementials, at least in their own envioroment, are cannibalistic. A large one will normally take pleasure in eating a smaller one, shredding it's soul and draining it's energy to feed itself and grow larger.For that reason, every elemential seeks power and energy.
The smallest ones are easy to summon as they normally are very pleased to get out of such a dangerous area. Fire elementials appear as small sparks, water ones as small globes of water, earth ones as small quartz rocks of roughly humaniod shape,air ones as tiny tornados.At this stage it is possible to trap or kill them.Nobody however would summon one to kill it, and only the more evil would trap them. If trapped, then if they ever escape they will try and kill the one who trapped them.
If *fed* with energy, or indeed, belief, they will happily carry out small jobs if not overworked.Slowly they grow to human sized.At this stage, many will leave, although there are those who are perfectly happy to continue working as it provides them with a decent *food* source.Most stay that size, but there are some that can grow bigger.
If through whatever reason an elemential can gather a human following, it will grow larger.Some at this stage will take their chances on the Planes, hoping to find and devour others of their kind.Others stay and encourage the building of villages and towns and if possible, cities.The larger the following, the larger the elemential.The bigger the elemential, the harder it is and the more dangerous and difficult it is to summon one.And a large one will demand something big in return for it's help.The largest ones, the ones who have founded a city, are almost impossible to summon and only leave the Planes when their cities are threatened by disaster or attack.
Water Elemential cities are at the mouths of rivers and have water running through their streets instead of roads (think of Venice IRL). They are often amongst the wealthest of cities as they control trade routes and charge a toll for those who would travel up or down the rivers.Hurricanes are rarely a problem as they attract air and water elementials which *eat* their energy. Floods can be a major hassle on occasion,however.And the cities, no matter which element they are loyal to, will sometimes make war on each other.
Earth Elemential cities are formed in mountian regions and control the seams of coal,gold,iron, silver and gemstones.Some are partly built within the mountians themselves, but most are not, as dangerous gasses can be a major hazard underground.Their roads are allways well built.