Others can recharge their strength using human emotions - Light ones from positive emotions, like joy or happiness, and Dark ones from negative ones, like hatred and pain. It is also able to raise the power level of any Other. This is of course, excluding the use of the Fuaran, a powerful magical book, which when used, may turn any number of ordinary humans into potential Others. Vampires and werewolves, lowest form of Others, are always Dark and they are the only kind of Others who are able to pass their abilities to ordinary humans - otherwise an Other cannot be made, only born. There are many different ways they can hone their abilities and specialize, both on the sides of Light and Dark. The Others live for centuries and can easily influence human minds, making people do their bidding.

The decision, once made, is final except in cases where an Other does an act of enormous light or dark, such as Merlin, or Arina. Each Other must either choose Light or Dark - usually they make their choice the first time they enter the Twilight and neither Watch may influence their decision. Both sides watch out for potential new Others, whom they can initiate into the use of magic. The Inquisition oversees both sides and prevents either side from gaining dominance, because, as noted in the twilight watch, dominance for either side means defeat for Others, serving to punish either side if they violate the treaty. Light Others created the Night Watch, to make sure that the Dark Ones keep the Treaty while the Dark Others created the Day Watch, to watch the Light Ones. The Treaty forces both sides to keep the balance on both sides and grants either side the right to an equal act of light or dark if either side uses their power on a human or other, and limits their actions. After realising that no side is likely to win, and that the world and ordinary people would suffer too much from magical wars, both sides signed a Great Treaty. They are opposed to each other and once they were at constant war. The Others are divided into the Light Others and Dark Others. The main mystery of the final novel is what is on the seventh level- only the greatest of magicians can penetrate to the seventh level. While the first levels are unpleasant and devoid of life (apart from blue moss in the first level), fifth and sixth levels are quite hospitable, with life and vegetation. While every Other may enter the first level, only the most powerful ones can get as far as the fifth, and the select few can get through to the sixth. The Twilight itself is divided into levels, with each level harder to access than the one above it. They can enter into the Twilight, a shadowy dimension next to our own, from where they also draw power to perform their magic. The entire saga is devoted to the Others - humans able to draw on the magical force flowing through the world.

Night Watch by Sergei Lukyanenko