The Elements are possibly the single most important aspect of magic. Certain creatures can withstand certain elements while others cannot.

Natural Elements
These elements are those which make up nature and its cycles. They are controlled mainly by Wizards

Fire: Seemingly everyone's favorite element (though I despise it), Fire is irrepressible, hot, and wild. The spirit of Fire is courage, and many fear its destructive capabitlities. However, Fire is not merely a destructive force, it is also a cleansing force. It destroys all that is old, making way for newer life to flourish in its place.  Creatures that live in the cold, plants, and beasts of Ice all hate Fire. The Undead, being incapable of regenerating their flesh, also hate Fire. Beasts of flame, as well as many others love it, while Mehanicals are virtually unaffected by it.

Ice (Cold):  Cold is the absence of Heat. Cold is unfeeling and cruel. The spirit of Cold is Repression, as it stops all life in its path, holding its seeds to the ground. Only the strongest of life forms can thrive in the Cold. Plants, Beasts of Flame, and tropical creatures all hate Cold. Yetis and their kin, as well as other creatures that live in the snow, love it. Mechanicals are undaunted by its onslaught.

Lightning (Electricity): Electricity is the force that binds together the physical world. Electricity is fast and tingly. Even lifeforms require it and generate it in order to survive. The spirit of Electricity is bonding and completion for even at the lowest level electrons hold molecules together. It can be directed through objects (metals mainly), or it can build in one place, then discharge, giving off tremendous heat and melting oblects that can normally contain it. Mechanicals and water creatures can be hurt very badly by it, while the Undead and creatures of stone are unaffected. However, Thunder in small amounts can actually aid Mecanicals by giving them a temporary boost similar to Bloodlust.

Earth: Earth is the womb from which all life comes forth. Earth is caring and protective. The spirit of Earth is hope. However, it is also a corrective and equalizing force, such as earthquakes (tectonic corrections) and acid/base reactions (ph equalization). Creatures that come directly from stone, as well as plants and those who burrow in the ground love it. Large creatures hate it. Those who fly are entirely unaffected by it, except when they crash into mountains :).

Water: Water runs through all living things. It is the preserver of life and the cause of rot. The spirit of Water is wisdom.