The Wraith are a fairly new species. They arose from a predatory insectoid creature native to the Pegasus galaxy -- known as the Iratus Bug -- that fed off human beings. Somehow, a sort of hybridization occurred between the Iratus Bug and the humans it preyed upon, giving rise to the Wraith, although the details of how this happened are still unknown.
Eventually, using some Ancient information and technology, the wraith grew in strength and power. Their feeding habits brought them into conflict with the established Ancients, resulting in a war that the Wraith eventually won by attrition, establishing thems as the dominant civilization in the Pegasus galaxy thereafter.
Wraith are humanoid creatures that are discernable from regular humans by a pale complexion, slitted eyes, markings on the cheek, sharklike teeth, and an unusual organ on one of their hands. Wraith possess superhuman strength, durability, and regenerative ability, and they are effectively immortal in terms of life expectancy. Wraith possess psionic abilities, including telepathy and the ability to project illusions. Being a human-derived species, Wraith share much of their genetics with humans.
A primary attribute of the Wraith is the need to feed. Every few months an adult Wraith needs to feed from a human. This is done by applying their specialized hand to the victim's torso and draining the "life" out of them. Wraith feeding results in accelerated aging and can easily be fatal. It also allows a deep probing of the mind of the victim and (because the process is intensely painful) can be used as a method of torture. The mechanics of the process are unknown. Adult Wraith have digestive tracts and can eat regular human food, but they require no other nourishment beyond human life-force and only eat for enjoyment. Wraith children, however, draw their sustenance by eating food until puberty.
Wraith society is divided into different Hive Ships, each being an independant state with it's own established "feeding grounds" (areas in which human civilizations exist for harvesting) and military forces. They do co-operate to eradicate established threats, but should their feeding grounds be insufficient, they are quite willing to fight among themselves. Besides harvesting, the Wraith generally allow civilizations in their feeding ground to grow on their own accord, so long as they don't pose a direct military threat, at which point the Wraith eradicate them via orbital bombardment, making human civilizations in the Pegasus Galaxy extremely wary of Wraith attack and generally limiting their technological development to pre-industrial levels.
Although little is known about the exact workings of their societies, Wraith government seems to be matriachal. The population reportedly includes a specialized class of engineers and technicians to maintain their spacecraft, as well as clear differences between Wraith administrators and field officers and soldiers, which implies a fairly regimented society with little if any internal mobility, although specific details involving this have not yet been revealed. They keep staffs of human slaves for various tasks (typically personal attendants) aboard their hive ships.
Due to the size of the current Wraith population, the Pegasus Galaxy's human population even at its peak is not enough to sustain the entirety of Wraith civilization continuously. To deal with this problem, the Wraith spend most of their time dormant in century-long periods of inactivity. The hive ships operate under the care of a small staff of custodians until the human population of the Pegasus Galaxy reaches a critical mass, at which point the Wraith population awakens to harvest. This cycle can be triggered prematurely, the Atlantis Expedition did accidentally. Should the human population be insufficient to provide adequate sustenance for the whole Wraith population at harvest time, the Hiveships will fight with each other over the resources available.
Due to their need to feed, the Wraith are a direct threat to any human civilization that they encounter. When the Wraith discovered the human presence in the Milky Way galaxy on Earth and various former Goa'uld controlled worlds, they dedicated themselves to developing intergalactic travel to move upon what is to them an extremely ripe and fertile feeding ground.
While in terms of simple numbers the Wraith are the dominant power in the Pegasus galaxy, they suffer from a number of fundamental flaws. Wraith spacecraft have to take periodic drops out of hyperspace, at which point they are vulnerable. The Wraith also lag much in shielding technology and are unable to create shield bubbles around their capital ships; this makes them vulnerable to having explosive ordinance teleported onto their ships via Asgard teleportation technology, although they have some defense against such moves using jamming systems.
Wraith of Note
- various Wraith Queens