Chapter

The Chapters of Gallifrey — often called ruling Houses or colleges — were the Great Houses closest to the Lord President. (PROSE: Lungbarrow, The Book of the War, The Ancestor Cell) Each Chapter was represented in the Time Lord Academy by a college bearing their name, (PROSE: A Brief History of Time Lords, The Ancestor Cell) such as the Prydonian Academy (PROSE:  Revelation) and the Academy of the Patrexes. (PROSE: Damaged Goods)

Many of the ruling bloodlines had sub-lines dedicated to exploring particular genetic philosophies. (PROSE: The Book of the War) The Doctor and Romana were both members of the Prydonian Chapter (TV: Extremis, PROSE: Shada) despite also belonging to Houses Lungbarrow and Heartshaven, respectively. (PROSE: Lungbarrow, AUDIO: Panacea) According to Commander Hallan, marriage was a way of strengthening the bonds between Houses and Chapters. (AUDIO: Spirit)

The heads of the Chapters were the Lord Cardinals, and the chief of these in a chapter was known as the Cardinal Prime. (PROSE: Lungbarrow)

The original Chapters
Each college was founded by one of the six legendary founders of Time Lord society, (PROSE: The Ancestor Cell) who were present at the anchoring of the thread. (PROSE: The Book of the War) They included Rassilon, Omega, Pandak, Apeiron, and one other, as well as possibly Eutenoyar. (PROSE: The Infinity Doctors, The Ancestor Cell)

The most prominent of the original Chapters was the Prydonian Chapter, whose members included more Lord Presidents than any other Chapter. Its significance was closely followed by the Arcalian and Patrex Chapters. (TV: The Deadly Assassin) The Dromeian, Cerulean, (PROSE: Lungbarrow) and Scendeles Chapters were overshadowed by the others. (PROSE: The Ancestor Cell) These original ruling Houses were almost indistinguishable; The Book of the War said the members of all six were "equally pale and complacent". (PROSE: The Book of the War)

House Ixion and House Catherion were ruling Houses that began a slow decline after the anchoring of the thread and the ensuing Diaspora. They were eventually replaced by House Mirraflex and House Lineacrux. (PROSE: The Book of the War)

Ceremonial colours
Each Chapter had its own dominant colour and wore robes of that colour during ceremonial occasions, such as the inauguration of a new Lord President. Prydonians used scarlet and orange. Arcalians used green. Patrexes used. (TV: The Deadly Assassin) Dromeians used silver-grey and Ceruleans, as the name would indicate, used blue. (PROSE: Lungbarrow) The Scendeles ceremonial robes ranged from a light pink to a darker shade of red. (PROSE: The Ancestor Cell) The colour gold was reserved for the Gold Usher. (TV: The Deadly Assassin)

During the War
During the War, political upheavals and social reforms on the Homeworld led to almost continual replacement of the ruling Houses as Newblood Houses were founded and other Houses rose and fell in importance. By the War's fifieth year, the six ruling Houses were the three traditional, political Houses Dvora, Tracolix, and Lineacrux, along with the three military Houses Arpexia, Xianthellipse, and Mirraflex. (PROSE: The Book of the War)

Behind the scenes

 * House Ixion and House Catherion were two ruling Houses before the anchoring of the thread; they went into a slow decline and were eventually replaced by Houses Mirraflex and Lineacrux. This suggests that some of these ruling Houses are renamed versions of the Chapters from TV: The Deadly Assassin. House Dvora, which Morbius, Romana, and the Master are all hinted to be a part of, was hinted to be the "scarlet chapterhouse" in AUDIO: A Labyrinth of Histories.

Capítulos de Gallifrey