Doral is a humanoid Cylon (designated model Number Five) who first appeared as a civilian public relations specialist aboard Galactica just prior to the Cylon attack on the Colonies. Through conversation with the projection of Cylon agent Number Six, Dr. Gaius Baltar notices a Cylon Device attached to Galactica's DRADIS station and convinces himself Doral is responsible, as he can freely enter the room while not having much business in it; he claims he has lab test evidence that Doral is a Cylon spy and has him thrown in the brig. He can then justify the finding of the Cylon device, alleging that the prisoner seemed very interested in that piece of equipment. Doral emphatically denies being a Cylon and claims to be from the village of Oasis, outside Caprica City, and having been on Kobol College on Gemenon. However, not willing to take a chance, Doral is abandoned by Commander Adama on the Ragnar Anchorage weapons depot before the fleet leaves the system. The audience is shown that Baltar was correct in assuming Doral a Cylon, as a copy of Doral, along with several copies of Number Six, Leoben Conoy, and Sharon come to his rescue. (In the novelization, Doral is a sleeper agent - he does not know he is a Cylon until the others come for him at Ragnar Anchorage.)
Doral appears again on Cylon-occupied Caprica curiously monitoring the situation developing between Sharon and Karl "Helo" Agathon. He initially decides that Sharon cannot be trusted, and orders Number Six to deal with her. Once Doral discovers that Sharon is pregnant, he states the child is a miracle, and must be protected at all costs. The discovery also leads to his suggesting a major tactical change, although the details of this new plan, as well as whatever changes were made from the original, have as yet to be clearly defined in the series.
The Doral Cylons seem to act more covertly, having an unassuming "average" appearance in order to better blend in with more trivial background matters instead of taking more noticeable positions of authority and purpose. He seems to have a position of authority among the Cylons, acting as overseer, and having a hand behind their decision making and tactical planning. This personalization is contradicted, however, in the special TV movie "The Plan," in which a copy of Number One/John Cavil berates a confused Doral copy (wearing clothing nearly identical to the first copy encountered by the Colonials) for his lack of disguise and caution while wandering the halls of Galactica. A later scene shows a small group of Doral copies assigned to menial labor disposing of masses of human corpses on occupied Caprica, doing work they complain is below them and should be handled by Centurions. Likewise, in the episode "Downloaded," a copy of Doral can be seen serving drinks to other humanoid Cylons. These scenes seem to imply the Doral models are of lower intelligence than other Cylon models, and possess less authority. Of the several Cylon infiltrators whose failures are listed by Cavil and "Tough Six", including the Number Eight known as Lieutenant Jr. Grade Sharon "Boomer" Valerii, the Number Two known as Leoben Conoy, the Number Six known as Shelly Godfrey, and the Number Four known as Simon O'Neill, Doral is the only one whose failure to complete the Cylon plan was not due to love but simply to blowing himself up before reaching a critical area of Galactica.
The Doral Cylons appear to be more fanatical, militant and cold-hearted than the other humanoid Cylons encountered thus far, short of the often vile, overtly vicious Brother Cavil. They calmly discuss the genocide of mankind (stating on one occasion "They [humans] would have destroyed themselves anyway. They deserve what they got."), and unhesitatingly conducting (on at least one occasion) a suicide bombing aboard Galactica. On the other hand, Doral was highly critical of the human suicide bombers in "Occupation" who inflicted Cylon casualties and fatalities, lambasting them for a 'lack of nobility'. Doral's violence is such that he held a gun to Gauis Baltar's head and forced him to sign a document allowing mass executions. He then murdered a copy of Six when she tried to stop him, proving that Doral is deeply hypocritical in his belief. In "Torn" a Number Eight accuses Doral of "barely even being able to say [God's] name." Number Fives are the only humanoid Cylon model not shown in a romantic or sexual relationship at some point in the series, although a Five in the episode "Tigh Me Up, Tigh Me Down" "can't help wondering" what it would be like to feel as intensely as Helo does for Sharon, noting that "even in his anguish", after Sharon was taken away as part of a trial of Helo's love, "he seemed so... alive", and a Five speaking with former Galactica deckhand James "Jammer" Lyman in detention on New Caprica in a Battlestar Galactica: The Resistance webisode tells Jammer that "a wife, kids, a life" is possible for him, and for the Five himself and "all of us", if he starts cooperating with the Cylons.