-Nature was designed to be balanced. Water and Fire, Light and Dark, Sun and Moon.
Echo and Kian Haeream were the physical manifestation of balance. The twins kept the scales of the supernatural world even. They represented the good and the bad, the compassionate and the merciless, the wise and the foolish.
Hybrids were creatures that were not suppose to exist in the natural order, so the miracle birth of the twins had tipped the scales. In order to have lived they had to set the scales back, so they became the balance.
For sixteen years the twins kept the balance, but when they get a message from their uncle, calling them back to their home, will they keep the balance or will they tip over into chaos?
[ Teen Wolf: Seasons 1-2]