The 4 elements
The legend tells that years ago 4 powerfull kings rulled the earth, Fire, Water, Air and Earth. They swore to protect the human race against the giants. And so they did, until one day a very powerful giant persuaded Fire of fighting by their side, he tricked him, gave him everything he ever wanted, he was the king of the giants.
There was a big war, which lasted a hundred years and a hundred days. The giants fighted by Fire's side, their king.
The 3 kings won, Fire asked for Mercy, he knew he made a mistake. But they locked him on a magic jar, so he could never get out.