The first book in the series, Gate of Ivrel (1976), was Cherryh's first published novel, and was followed soon thereafter by Well of Shiuan (1978) and Fires of Azeroth (1979). These three works have been subsequently released in omnibus editions under various titles, including The Book of Morgaine, The Chronicles of Morgaine, and The Morgaine Saga. In 1988, Cherryh published the fourth book in the series, Exile's Gate.
In the 1980s, Jane Fancher began a graphic novel adaptation of Gate of Ivrel in close collaboration with Cherryh. Although it was never completed, Fancher self-published one segment of the work with a color cover and black and white interior art entitled C. J. Cherryh's Gate of Ivrel No. 1 (1985). Two parts of the adaptation were subsequently published as full color versions by The Donning Company under its Starblaze Graphics imprint: Gate of Ivrel: Claiming Rites (1986) and Gate of Ivrel: Fever Dreams (1987). In 1987, Tor Books published an interactive novel set in Morgaine's universe, The Witchfires of Leth.
This series has been identified as being set in the Alliance-Union universe, as it is stated that Morgaine was sent on her quest by the "Union Science Bureau".
Because of the temporal paradoxes involved in time travel, the gates are a threat to universal causality and therefore to the future of innumerable worlds. In fact, as presented in the backstory of the Cycle, unwise use of the gates' temporal properties has already decimated at least one highly advanced civilization, the qhal. To prevent additional such calamities, Morgaine is engaged on a centuries-long quest that takes her from world to world via the gates, setting each gate to self-destruct just after she has used it to move on to the next. It is not clear from the storyline how long Morgaine has been traveling, but it is spelled out that she was sent by the Union Science Bureau as a member of a task force one hundred strong given the mission of destroying the gates. There has been attrition over time, with an act of treachery prior to the first novel leaving Morgaine the sole survivor.
The gates and other items in the stories are based on advanced technology, and there are no magical or supernatural elements presented, so the works can be properly classified as science fiction. But the books feature several tropes common to fantasy, including medieval-type settings and low levels of technology on the worlds depicted in the novels, a feudal-like relationship between the main characters, and medieval-style warfare and weaponry.
The device Morgaine uses to destroy the gates, for example, though it incorporates advanced technology, has the appearance of a sword. In the tradition of heroic-epic swords, it has its own name, Changeling. This blending of technology and elements more common to fantasy often results in the books being labeled as works of "Science Fantasy." Indeed, on the author's own Web site she lists them under the heading of "Fantasy Novels," not "Science Fiction." The stories have also been identified as Heroic Fantasy, and earned Cherryh membership in the Swordsmen and Sorcerers' Guild of America (SAGA), a literary society that recognizes notable achievements in heroic fantasy fiction.
Another theme is the status of the ruined alien race, the qhal (the name and its derivatives are spelled differently on each world Morgaine visits: e.g. qujal, khal) in relation to human beings. The qhal had been the dominant species, but were ruined by their misuse of the Gates. (The Gates themselves are relics of a more ancient, vanished race, of which it is revealed in the fourth book of the tetralogy, Exile's Gate, Morgaine is a descendent through her father.) All the worlds described have both qhal and human inhabitants, and are at a quasi-medieval level of development (travel is by foot or on horseback, for instance), with advanced technology present but more or less hidden. It is not always explained where the human populations have come from. In Gate of Ivrel, among the ruined human principalities of Andur-Kursh, qhal are hated and feared and few survive, though they remain powerful. In the slowly-drowning landscape of Well of Shuian the qhal are the dominant, cultured society and humans live in miserable squalor. In the forest world of Fires of Azeroth, qhal and some humans have learned to live in mutual respect, carefully tending their environment (which includes another sentient race, more obviously alien): this paradisial arrangement is threatened by the irruption of the aggressive qhal-human host of refugees from Shiuan. In the world of Exile’s Gate, a dominant qhal society keeps the human-populated areas subject through qhal governors - the exiles from the Lord's court - who have been forced to take human form.
A third theme is the mystery of Morgaine’s own species identity. She resembles the qhal, being tall and slender with long fair hair and pale eyes and skin, but maintains she is not qhal. She finally admits to her companion Vanye in Fires of Azeroth that she is a half-breed, with a human mother and a father from the race preceding the qhal, who built the gates. She may have killed her father, perhaps as an early part of her mission. Isolated members of this immensely ancient race still survive, such as the Lord of the world of Exile’s Gate.
The mystery surrounding Morgaine is increased by the fact that, perhaps uniquely among Cherryh’s major protagonists, we never see the action through her eyes. She is always observed by others, and she is not much inclined to talk about her origins, her purposes or her motivations.
Chief among those who observe her, and receive a slow series of revelations on these matters, is her faithful vassal and companion, Nhi Vanye, the bastard son of one of the lords of Andur-Kursh, and therefore a man whose original culture makes it hard for him to comprehend the advanced technology with which, and against which, Morgaine makes war. Outcast as a brother-slayer from his own land, he is ilin, a masterless, homeless warrior akin to the Japanese ronin, when they first meet. By accepting food and shelter from her, according to an ancient Kurshin rite, he is obliged to provide a year of service to her. The stubbornness and exaggerated sense of honor associated with his people prevents Vanye from breaking his commitment, even when she makes seemingly-impossible demands of him.
Though she frees him from his servitude at the end of Gate of Ivrel, he follows her through the gate to Shuian, and their relationship strengthens and deepens. They come to love one another, but the experience is often painful and confusing. Unlike most genre fantasy, the narrative dwells much on the exhaustion, discomfort, pain and fear of their presumably endless quest. At an early stage, Vanye begs not to be told many things Morgaine would be willing to communicate to him, which retards the pace of revelation further. In all four novels, Vanye is separated from Morgaine and has to fend for himself among enemies, not knowing if she is still alive or will pause to come back for him, with a concomitant increase in dramatic tension. Vanye’s uncertainties are one of the chief strategies Cherryh employs to keep the reader in a parallel state of uncertainty.