Ultranauts

Ultranauts are a faction of transhuman spacefarers. The majority of Ultras who appear in the books have opted for extensive and obvious mechanical modifications, replacing their original limbs and organs, but while this is their most obvious and apparently widespread trend, not all Ultras utilise such modifications. Ilia Volyova, one of the central Ultra characters of the books, has no obvious modifications and is still described as an Ultra, while in Chasm City other characters such as Zebra, who have opted for extreme body modification, are not described as such, indicating that the term may refer either to something biological that is shared by all Ultras, or may possibly be an honorific for those who have served as crew aboard a lighthugger. In The Prefect, it is stated that an Ultra can look fully human "and yet be crawling with furtive and dangerous machinery." All the Ultras encountered in the books have lived long lives, partly due to long periods of cryopreservation or "reefersleep" during interstellar transit, partly due to the time-dilating effects of near-lightspeed travel, and partly due to their willingness to replace failing organs and limbs with mechanical alternatives, but possibly also due to genetic modifications intended to fit them for space travel.

In Revelation Space, a quirk of Ultra society is described (referred to again in Diamond Dogs); for each session in reefersleep, they grow and maintain a dreadlock as a badge of their status, although they are also described as using these status symbols as stakes in gambling games, and once again, Ilia Volyova, although an Ultra, does not sport these dreadlocks. Aesthetics do appear to be of greater concern to most Ultras than more pragmatic concerns such as functionality and reliability. Some of the more extensively modified Ultras described in the books have, apparently intentionally, turned themselves into living sculptures.

Unlike other factions in the Revelation Space universe, such as the Conjoiners and Demarchists, there appears to be no unifying political structure or philosophical school of thought behind Ultra society. Although extremely isolated from the rest of humanity during their long voyages, they do not appear to form particularly close associations even within crews; for the crews of the Nostalgia For Infinity (Revelation Space) and of the Gnostic Ascension (Absolution Gap), power struggles and mistrust are presented as the normal state of affairs. However, neither crew is exactly normal; shipmaster Inigo Standish in Galactic North comments that Ultras like these crews are a minority.