The Watchers are a vastly powerful, ancient extraterrestrial race who untold eons ago undertook the task of passively observing the phenomena of the universe. Their homeworld is an unnamed world in an unknown solar system in another galaxy than the Milky Way which is covered with lush vegetation and bears no artifacts of habitation. None of the Watchers live on their homeworld anymore, having taken up permanent residence somewhere within the solar systems they have elected to observe. On the rare occasions that the Watchers convene on their homeworld, they use their advanced technology to create temporary dwellings which they disassemble after use. It is improbable that the planet the Watchers call their homeworld is their planet of origin. If it were, the age of the race would be relatively brief, a fraction of the lifespan of a single solar system still in the main sequence of its existence. Because the Watchers are scattered across the universe, it is impossible to calculate how many of them there are.

Each Watcher possesses vast mental, physical, and energy-manipulating powers. Watchers are telepathic, able to scan the mind of virtually every known form of sentient life and to project their thoughts into any brain. Watchers can alter their appearance at will, assuming any guise they so choose. This is apparently a mental/psionic capacity, and not a physical shape-shifting ability like that of the alien Skrulls. Watchers can convert their bodies into some form of energy in order to "teleport" through space at hyper-light speeds. (It is probably that they traverse warp space to do so.) Watchers can also psionically manipulate energy in the electromagnetic spectrum. The limits of this capacity are not known: it is probably on the same basic level as such Earth gods as Odin and Zeus or such alien races as the Elan. Watchers are seemingly immortal (although degrees of maturity are evident), having bolstered the limits of their life forces with "delta-rays." Presumably an explosion that dispersed all of their bodily molecules thousands of miles would prove fatal. There appear to be no secondary sex differences between male and female Watchers. Watchers still reproduce sexually, however, and rudimentary family relationships still provide care and training for their young,

The Watchers undertook their mission of passive observation untold eons ago after an experiment in altruism ended in tragedy. Soon after the Watchers attained virtual immortality and mastered such disciplines as converting themselves to energy for interstellar travel through hyperspace, the Watchers' High Tribunal dabated whether or not their race should share its high technology with the less advanced civilizations of other worlds. The Watcher named Ikor, stated that it was their race's duty to help other races, although the Tribunal's leader, Emnu, argued that the Watchers owed nothing to races that he did not regard as their equals. It was Ikor's son, Uatu, who finally persuaded the majority of the Tribunal to side with Ikor on the issue.

A delegation of four Watchers, including Uato, set forth from their world and traveled to the first planet bearing intelligent life that they came upon the planet Prosilicus. The Watchers offered the Prosilicans knowledge of atomic energy, a rudimentary science for the Watchers, but one that would advance the Prosilicans' level of technology considerably. The Prosilicans readily accepted the Watchers' gift and were tutored for some months by them on its applied uses. Their test mission accomplished, the four Watchers left the planet.

The Prosilicans developed nuclear weaponry, which they first used in wars on their own planet. They next engaged in all-out war with another alien race, and as a result, the planet Prosilicus was devastated, and its people brought to the point of extinction. Years after they had lift, the Watchers returned to Prosilicus to check on its people's progress, and were horrified to see the results of the nuclear conflicts. On the basis of this one test, the Watchers decided never again to interfere in the affairs of any other race. The shame of the Prosilicus experiment was, in the Watchers' view, so great that they devised a code of ethics of strict non-interference and passive observation. This code is so strict that if a being of another race were to be dying at a Watcher's feet, the Watcher would not presume to disturb the order of the universe by offering the being aid. Rather, the Watcher would simply record the being's death throes.

Soon after the experiment, the race of Watchers evacuated their homeworld; and relocated throughout their galaxy and neighboring ones. Each Watcher chose as his or her new home base a solar system where intelligent life had evolved or was in the process of doing so. Acutely motivated by the pursuit of knowledge, the Watchers undertook the observation of the universe (with emphasis on the intelligent races therein), recording mentally everything they witnessed for the sake of eventually sharing it with their fellows.

The first Watcher ever encountered by inhabitants of Earth was Uatu, the Watcher posted in our solar system. It is not known precisely how long Uatu has been observing Earth; his presence is believed to predate the rise of humankind. Uatu resides in the Blue City on Earth's moon, an abandoned settlement with its own atmosphere built by the alien Kree several million years ago. The Blue Area was also occupied by the Earth-born Inhumans. The first known encounter between Uatu and an Earth being occurred when Reed Richards and the Fantastic Four traveled to the moon to investigate the Blue Area and found themselves in battle with the Red Ghost. The Watcher compromised his vow of non-interference by appearing to the Earth beings and allowing them to retain their memories of his existence.

Having once violated the spirit of his peoples' oath, Uatu began to violate it in deed. For unfathomable reasons, he began to develop a fondness for the Fantastic Four, and began warning them of menaces to Earth. At the wedding of Reed Richards, Uatu even helped the Fantastic Four's leader attain victory over the horde of enemies who threatened the occasion. When the world-eater Galactus came to Earth for the first time, Uatu went so far as to try to hide the planet from Galactus's surveillance, face him to debate why the Earth should be spared, and sent one of the Fantastic Four to Galactus's home base to acquire the weapon that would defeat him. As Uatu later explained when he was brought on trial for his numerous violations of his peoples code of ethics, he had allowed himself to identify with the action and emotion that he observed, and yearned to become involved. After his first fateful violation, further transgressions became easier to justify as he aided his favorite heroes, the Fantastic Four, and marked important events in Earth's history. Uatu finally disgraced himself completely by physically opposing the Kree warrior Captain Mar-Vell. On trial for his deeds, Uatu was released under his own cognizance, vowing not to transgress again. Although he has not committed any overt violations since then, he has made his presence known in several critical situations, thereby arguably affecting the incidents' outcomes.

In recent years, Uatu has expanded the scope of his observations to include alternate realities whose events diverge from those of the reality in which he lives. The precise manner in which Uatu makes these observations, as well as the circumstances of his discovery of these alternate realities has yet to be learned. The Watcher uses these glimpses into divergent worlds to give him insights about the "real" world.

Other then Uatu, only a few other Watchers are known by name. There is Ecce, the Watcher who witnessed the incubation and hatching of Galactus, and had the opportunity to destroy the future world-eater but did not act upon it. There is Ikor, father of Uatu, the Watcher who proposed the Prosilicus experiment and in penance drafted what became the Watchers' code of ethics. There is Emnu, leader of the Watchers' former world council (now called the High Tribunal), who had opposed the Prosilicus experiment and is now the supreme authority on the rare cases where violations of the Watchers' oaths are brought to trial. Finally, there is Aron, a young Watcher who has not yet been assigned a solar system to observe.

First Appearance: (of Uatu) FANTASTIC FOUR #13, (of the Watchers) TALES OF SUSPENSE #53