The Tribes series is set in a distant future, spanning from 33rd to 40th century AD, while the back-story of the games begins in 2471, when a scientist Solomon Petresun invents the first "cybrid", a bio-cybernetic hybrid artificial intelligence named Prometheus or IT. Based on ITS design, thousands of cybrids are mass-produced as slaves for the mankind, however, by 2602, Prometheus grows wary of humans and rallies all cybrids produced to date against humanity in a devastating slaughter later named The Fire. The events of The Fire are depicted in Earthsiege (1994), the precursor of the Tribes series, although several important points (such as the appearance of Petresun and Prometheus as the factions' leaders) were retconned later in Starsiege.
In Starsiege continuity, the Terran resistance manages to drive Prometheus' initially victorious forces out of Earth and onto the Moon where they are consequentially decapitated by General Ambrose Gierling and his squad's suicide attack on the cybrid base in 2627. Prometheus, however, survives the explosion and to counter this threat, Petresun (having technically achieved immortality through his studies) proclaims himself the Emperor of Mankind in 2652 and succeeds in unifying and rebuilding the Terran civilization. Pursuing his goal of fortifying the Earth against the inevitable cybrid retaliation, Petresun ruthlessly exploits Martian and Venusian colonies, spawning massive resistance movements among the colonists by 2802. The Martian rebellion led by the former Imperial Knight Harabec Weathers and the consequent Cybrid Wars are described in Starsiege (1998).
The chronologically first game in the Tribes series is Tribes: Vengeance (2004). Set some time between 33rd and 40th century, it shows the Great Human Empire, now ruled by "Imperial King" Tiberius, having hunted down (almost) all remaining cybrids and expanded beyond the boundaries of the Solar system through the so-called Interstellar Transfer Conduit. While the Empire itself is prosperous, there are outcasts, known as "the Children of Phoenix" (after Harabec "Phoenix" Weathers, whom they consider their progenitor) or simply Tribals. Their insubordination has made the Empire dispatch a great force of elite Imperial Knights, the Blood Eagles, against them, however, by the time of Tribes: Vengeance, the Eagles have fully embraced the Tribal way of life, considering themselves Tribesmen despite still having ties to the Empire.
The next (chronologically) game in the series, Starsiege: Tribes (1998) sees the conflict between the Blood Eagles, the Children of Phoenix, and other tribes formed by the renegades of these two (such as the Star Wolf and the Diamond Sword) escalating into countless blood feuds before finally culminating in the devastating Tribal Wars about 3940. The sequel, entitled Tribes 2 (2001), deals with the insurgent uprising of BioDerms, a new race of warriors/workers created by the Empire to replace the cybrids, and their assault on the Wilderzone, the space frontier where the Tribes mostly reside. The Tribes Aerial Assault (2002) does not significantly contribute to the fictional setting of the series.
Content added from wikipedia