The Corsair

The Corsair was a Renegade Time Lord, described by the the Eleventh Doctor as "one of the good ones". The Corsair took on different genders throughout its many regenerations.

Biography
This incarnation of the Corsair was described by Auntie as "a strapping big bloke." The Corsair's left arm had been stitched onto the composite humanoid being known as "Auntie" that served as House's slave. The other composite humanoid slave, "Uncle" received "the spine and the kidneys." The loss of these organs was presumably lethal and the Corsair went the way of House's numerous other Time Lord victims. (DW: The Doctor's Wife)

The Doctor discovered the Corsair's fate after being contacted by his hypercube and following its psychically encoded distress message to House. (DW: The Doctor's Wife)

Behind the scenes
On his blog, Neil Gaiman stated that before he began writing the first draft, he wanted to make sure the idea of the Corsair was okay with 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 in which the Doctor talks about the Corsair. 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 asked the Corsair if he could travel with him and act as his "assistant", but the Corsair just laughed. Steven 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".

The Brilliant Book 2012
According to The Brilliant Book 2012, a non-canonical REF book: amongst its missions for the Time Lords, the Corsair stole the Callisto Pulse from the Callistan Kleptocracy.


 * Though it is not specified, this implies the Corsair was an agent of the Celestial Intervention Agency.

Although she denied ever having fought the Daleks, she was spotted in her seventh incarnation on Clarkor Nine when the Dalek scout ship arrived. It is highly likely that she was involved in those Daleks having their suction-cups and manipulator arms removed in the night and fused into a shape resembling a Skarosian profanity.

He had visited Earth several times. He was worshipped as a god by the Assyrians until he became bored and departed with the sacred temple cat.

The Doctor and Corsair had multiple adventures together, getting drunk in the Corsair's fourth, fifth and eighth incarnations. Each time, the Doctor swore never to do it again. Twice, they woke up in jail and the other time they woke up in the Bank of England vaults.

The Corsair was formally censured by the Time Lords after it 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's final adventure was when he was working on the Time Lords' Fourth Universal Survey. The Corsair was presumably killed by the entity known only as House, a disembodied being which fed on artron energy it harvested from captured TARDISes. He was in his ninth incarnation.

Gaiman expanded on the history of the Corsair in the The Brilliant Book of Doctor Who 2012, in which he indicates that the Corsair had a total of nine regenerations, several of which were female.