Children of the Moon

Children of the Moon, known more commonly as Werewolves, are a mythical species from the Twilight Saga. These mythological creatures happen to be immortal and they rarely travel in packs, unlike the Quileute shape-shifters. These creatures lack control over themselves when they are turned, during the full moon. The Children of the Moon are created after being bitten by another werewolf, and are not wolves because of their genes and ancestors or being the child of two werewolves. These creatures are not the same as the Quileute shape-shifters of La Push, since they turn into wolves at the full moon instead of anytime during the day. When the moon isn't really full, then the Children of the Moon are not turned into wolves.

They have been described as the only natural enemy of Vampires.

History
Not much is known about the Children of the Moon. It is known that Caius, one of the Volturi's leaders, is terrified of them because he was nearly killed in a fight with one a few thousand years ago. Aro and Marcus knew about Caius's encounter, and they began a war against the Children of the Moon because they pose a threat to vampires everywhere. In Eclipse, it also says that James hunted one across Siberia though he did not know it was a werewolf. The result of the war so far has been near extinction of the werewolves in Europe and Asia. It is unknown if they are found anywhere else in the world.

The Volturi refuse to tolerate truces or alliances between werewolves and vampires, the punishment for violating this law most likely being death. This was something that Caius tried to stress when the Volturi put the Cullen Family on 'trial' for creating an immortal child. But the werewolves the Cullens had allied with were really shape-shifters who took wolf forms, and the law therefore didn't apply.

Appearance and Traits
Due to the Volturi's initial assumption that the La Push shape-shifters were Children of the Moon, the Children of the Moon probably look very similar in appearance (when they are transformed) to the La Push Shape-Shifters. It can also be assumed that their abilities are similar as well. Although there is no more evidence to back these claims.

It is mentioned that Children of the Moon rarely form packs. It is not known if they possess similar pack qualities with the Quileutes, such as reading each others' minds and natural hierarchy, however, in Breaking Dawn, it was commented that true werewolves are disorganized compared to the shapeshifters, so it can be assumed that the mind-reading powers do not apply to actual werewolves.

A true werewolf has yellow eyes, which become more prominent during the full moon. Werewolves do not age, and have blood and a beating heart like humans, although they probably smell unappetizing to vampires. Werewolves consume flesh, human or animal. Like shape-shifters, werewolves probably have strength, speed, rapid healing, and heightened senses.

It was stated that Caius nearly lost a battle to a werewolf, namely, one werewolf; because of this, it can be assumed that werewolves are even more powerful than shapeshifters, who have to fight with vampires in packs to win the advantage.