Oldblood

"Oldblood" was an informal term for Time Lords of the oldest Houses. Compared to the Newbloods, Oldblood Time Lords were overly traditional and conservative to a fault, the definition of the Homeworld's stagnancy, and were always noted for being stereotypically elderly or impassive. The Oldbloods' were resistant to any form of change and were consistently at odds with the newer Houses, finding fault and suspicion with even the most traditionalist of their Newblood fellows. (PROSE: The Book of the War)

One of the most noted physical differences between the Oldbloods and the Newbloods was that the latter were Loomed with twin hearts. (PROSE: Christmas on a Rational Planet) According to one account, the First Doctor from the House Lungbarrow, one of the oldest Houses on Gallifrey (PROSE: Lungbarrow), would not have a second heart until after his first regeneration. (PROSE: The Man in the Velvet Mask)