The Corsair was a Time Lord adventurer and an old friend of the Doctor, described by the Eleventh Doctor as "one of the good ones." The Corsair changed gender a few times throughout their many incarnations. The Doctor noted with fondness that when the Corsair was female, "she was a bad girl." (TV: The Doctor's Wife)
Like all Time Lords, the Corsair was taken from their family at the age of eight, for the selection process in the Drylands. Staring into the Untempered Schism as part of a Time Lord initiation rite, the Corsair reacted by running away from what they saw in the Schism. (PROSE: A Brief History of Time Lords)
At some point in their lives, the Corsair left Gallifrey in their Type 60 TARDIS to travel the universe. They named the TARDIS Esperanza. (PROSE: One Virtue, and a Thousand Crimes) Each one of the Corsair's incarnations had the symbol of the Ouroboros tattooed somewhere on their body. It changed size each time with each different regeneration. Without it, they did not feel themselves. (TV: The Doctor's Wife)
At least one of the Corsair's incarnations was female. (PROSE: Keeping up with the Joneses) The Fourth Doctor once said to Romana II that he should meet up with the Corsair sometime, referring to the Corsair as both a man and woman when he did so. (PROSE: Shada) According to the Eleventh Doctor, the Corsair was a woman a couple of times, saying she was "a bad girl" each time. (TV: The Doctor's Wife)
The Corsair and the Doctor have ended up in jail cells on more than one occasion. The Thirteenth Doctor noted the last time the two of them had a drink together, the Doctor woke up in a bank vault. (COMIC: Old Friends)
Incarnations of the Corsair
In his final incarnation, (TV: The Doctor's Wife) he was described as a "strapping big fellow" with "a trustworthy face". (PROSE: One Virtue, and a Thousand Crimes) The Corsair went the way of House's numerous other Time Lord victims who had fallen into House's bubble universe and was marooned when his TARDIS was drained of energy. The Corsair had only just enough time to get a message together before he was finally killed. (TV: The Doctor's Wife)
In one account of events of the rediscovery of Shada, the Fourth Doctor mentioned the Corsair while he and Romana II mused over Time Lords who broke with traditional Gallifreyan inactivity, considering him "one of the good 'uns" and desiring to catch up with her. (PROSE: Shada)
Behind the scenes
The Brilliant Book 2012
In The Brilliant Book 2012, a book that contains non-narrative information, Neil Gaiman provided more information in "Eleven Things You Probably Didn't Know About the Corsair".
Specific attributes and details about the Corsair's incarnations were first provided in The Brilliant Book 2012:
- Third Corsair: Had a multi-coloured Ouroboros tattoo on their back, the largest version of the tattoo.
- Fourth Corsair: Male incarnation who got drunk with the Doctor.
- Fifth Corsair: Female incarnation who got drunk with the Doctor. She had the smallest Ouroboros tattoo, which was the size of a ten pence piece on her upper thigh.
- Eighth Corsair: Male incarnation who got drunk with the Doctor.
Additionally, seven images of the Corsair's incarnations are provided, albeit unnumbered:
- A bearded man with a top hat. Tattoo on the back of the neck.
- A person with a bowler hat and a cane topped with an hourglass. Ouroboros on the back of the trenchcoat.
- Light-skinned arm with a sonic screwdriver-like device. Tattoo on the inside left wrist. (Closest match to the Corsair's arm in The Doctor's Wife.)
- A dark-haired woman in a black dress. Tattoo on the upper back.
- A dark-skinned arm with a parrot. Tattoo on the back right wrist.
- A person wearing a black coat and a tricorn hat.
- Dark-haired woman in red Gallifreyan robes and collar. Tattoo on lower right thigh.
- The Ouroboros tattoo trademark of the Corsair — a snake eating its own tail, symbolising eternity — moved around the Corsair's body with each regeneration.
- The Doctor and Corsair had many adventures together, getting drunk in the Corsair's fourth, fifth, and eighth incarnations. Twice they woke up in jail and once in the Bank of England vaults.
- Amongst their secret missions for the Time Lords, the Corsair stole the Callisto Pulse from the Callistan Kleptocracy. The Corsair denied stealing it and Time Lords denied asking him to steal it.
- They visited Earth several times. He was once worshipped as a god by the Assyrians but left with the sacred temple cat after getting bored.
- No matter which race or gender, the Corsair had an amazing and trustworthy smile.
- The Corsair preferred to travel alone, but liked having a cat or a parrot on his TARDIS.
- The Corsair was formally censured by the Time Lords after they may have been linked to the theft of the Portrait of Rassilon. This was overturned by Lady President Flavia, perhaps due to the Corsair's smile.
- The Corsair was not the only Time Lord to bear a snake tattoo on their arm. Whereas the Corsair tattooed an ouroboros on each of their new bodies, the Third Doctor had a tattoo of a snake in the shape of a question mark on his right arm. (TV: Spearhead from Space)
- On his blog, The Doctor's Wife scriptwriter Neil Gaiman stated that before he began writing the first draft, he wanted to make sure the idea of the Corsair was okay with series show runner Steven Moffat before he became fixed in the story, so he sent him an email with a piece of dialogue between the Doctor and Amy Pond in which the Doctor discussed the Corsair. In this draft, the Doctor explained that the Corsair did not have a name and used to travel, exploring the limits of time and space. The Doctor said that when he was twelve he had asked the Corsair if he could travel with him and act as his "assistant", but the Corsair had just laughed. Moffat replied that he wanted the Corsair to be less like the Doctor because the Doctor "does what he does for reasons too vast and terrible to relate." 
- According to Neil Gaiman, Russell T Davies saw the image of the Corsair's arm with a parrot and liked the idea that the Shopkeeper from Sarah Jane Adventures episode Lost in Time was actually the Time Lord known as the Corsair, although no in-scene references have been made.
- The Corsair, being the first confirmed example of a Time Lord changing genders on regeneration, was frequently cited in media and online discussions in 2013 as to whether any future incarnation of the Doctor could be played by a woman. The Doctor would not get a female incarnation until 2017, with Jodie Whittaker's Thirteenth Doctor.
- The Corsair's hypercube, with Ouroboros motif, was among the variants of toy hypercube produced by Character Options.