At the close of the New World War (NWW) the nuclear fallout was so extreme that even the elements themselves were mutating. Slowly at first because of the nuclear winter their growth has blossomed and spread during the nuclear spring. They have spread throughout the world, taking over cities the humans and ornithians have abandoned and making many of the old technologies inaccessible.
The base elementals fall under four categories, Earth, Air, Water, and Fire, but sometimes there are mix breeds of two different elements, creating things like Magma elementals (earth and fire) or Storm elementals (water and air). The different variations are depending on the concentrations of each. Any mixed elemental is generally outcast from the normal society and ostracized, making them none too common.
Tri-elementals (mixes of three) are quite rare, being thrown out from nearly all societies, but powerful enough that they are nearly completely solitary. Finally, there are Full-elementals, these are mixes of all four elements and are thought to be a myth, any scientific study to produce these creatures ended in disaster in the early tests, either failure or success, both being dangerous to everyone involved. They are highly intelligent and extremely powerful, but they keep to themselves. Below are descriptions of the base elementals.

Fire elementals:

The fire elementals are aggressive, ruthless foes. They sometimes attack without provocation, in large packs, decimating anything in their way. They reside in the centers of trade, away from large bodies of water and the mountains. They are largely regarded as the most dangerous of the base elementals, because of their aggressive nature. They do not give up easily and should not be messed with. They are largely influenced by the sun and are more prevalent during the summer.

Earth Elementals:

The earth elementals are very protective, territorial creatures. They do not attack unless they think that they are in danger, usually from intruders into their lands. They care deeply for their young and live in small, close knit packs, the largest being twenty deep at most. They reside in the mountainous areas, taking over any mountain cities that they could find but preferring to be separated. They are largely regarded as stupid, slow creatures, but they are extremely powerful and very vigilant. Unless they or one of their own are threatened they do not stray far from the mountains, avoiding the large bodies of water the most. They are more prevalent in the spring, as the plantlife begins to blossom/

Air elementals:

The air elementals are mischievous, nomadic beings. They fly around everywhere and are basically like poltergeists, messing with whoever and whatever they can get their hands on. They attack without provocation and definitely disrupt the trade business, anyone alone and in small numbers are vulnerable to harassment. They haven’t taken over many cities, enjoying their freedom more than anything. They are feared by the ornithians, and they take advantage of that at any chance. Being nomadic peoples one would never see them in groups larger than ten deep. They are more prevalent in autumn as the plantlife dies off and is swept away.

Water elementals:

The water elementals are quick to anger and quick to forget as well. They will attack you if they notice you but once you are away from them they completely forget you existed. They reside mostly around the coasts, though some of them are in the lakes and streams further inland. They do not care for the mountain lakes because they are surrounded by earth elementals. They do not travel inland unless there are floods and have occupied the majority of the coastal cities, save the ones that were held onto by the humans and ornithians. They are largely effected by the moon and are more prevalent during the winter.