13 was a prime number, (AUDIO: The Haunting) considered unlucky by the superstitious, (COMIC: Triskaidekaphobia) due to "mystic properties". (AUDIO: The Thirteenth Stone) Some people were beset by triskaidekaphobia, according to the Twelfth Doctor an irrational fear of the number 13. (COMIC: A Confusion of Angels)
In particular, the Triskaidekaphobes, a group of thirteen clones, feared the number above all else. Living, as they did, on the 13th moon of the 13th planet in the 13th Galaxy, they considered themselves the unluckiest people in the galaxy.
When the Tenth Doctor visited their moon with Rose Tyler, on the 13th day of the 13th year in the 13th century, a Friday, helped these unlucky individuals to overcome their run of bad luck by destroying Bob Kreesus' luck machine. They were also were struck by lightning and rained on by cats. (COMIC: Triskaidekaphobia)
- Main article: Life cycle
Time Lords generally had up to thirteen lives, as they were afforded twelve regenerations. (TV: The Deadly Assassin, The Five Doctors, AUDIO: Trial of the Valeyard) Some individuals, like the Doctor and the Master, were given additional regeneration cycles, to allow them to go on past their natural ends. (TV: The Time of the Doctor, The Sound of Drums) The High Council of Gallifrey were empowered to offer such individuals new life cycles. (TV: The Five Doctors)
The incarnation to come out of the Doctor's fourteenth regeneration was officially regarded by themselves to be the "Thirteenth Doctor" (although she was technically their fourteenth, due to their time war incarnation not being counted). (COMIC: The Many Lives of Doctor Who)
Behind the scenes Edit
The dialogue in A Confusion of Angels which elaborates on triskaidekaphobia was released in the final issue of Titan's ongoing Twelfth Doctor series — specifically Year 3 #13 — before the launch of the Thirteenth Doctor's own range.