Nightwatch Introduction (to the film)

Night Watch

The division of Light and Dark had always existed between the Others. Those of the Light believed it was their duty to help the weak and the helpless. Those of the Dark shunned all obligations. They did what they wanted, regardless of morals and consequences. For many millennia, the two sides fought a vicious battle. Both were willing to use any means necessary to achieve victory. Eventually they realized that if they continued their battle, neither side would survive.

The leaders of both sides forged the Grand Treaty—a set of laws to govern the way the Others used their powers. The Light Others created the Night Watch, the Dark Others the Day Watch, to ensure that neither side would violate the Treaty. The Inquisition, a group composed of both Dark and Light Others, was created to ensure that neither side became too powerful. If they spend them too quickly, the Others can use the feelings and emotions of the humans surrounding them to recharge their powers. The Dark Others use negative emotions such as pain or anger, the Light Others use positive emotions such as joy. Feeding on pain causes pain to increase, feeding on joy causes joy to wane. Because negative emotions are much easier to achieve in humans, this arrangement creates a situation where the powers of the Dark Others are easier to recharge and are much more readily available than those of the Light Others.

Since the signing of the Treaty, the Night Watch and the Day Watch have kept their eyes on each other, diligently policing every violation. The old leaders continue to plot, using humanity and the Others as their pawns. Only time will tell which side will prevail.

http://en.wikipedia.org/wiki/The_Night_Watch_%28Russian_novel%29