Four Names

The Four Names were the four mysterious Time Lords that Rassilon had instructed the Citadel's Watchmen to kill or assassinate, but only when the right time came. Rassilon's full reasons for fearing these four Time Lords was unknown, though Chancellory Guards and Watchmen Raimor and Peltroc knew Rassilon's fears regarding the fallibility of the Time Lords, stating he knew who the "real enemy" was. (PROSE: The Infinity Doctors)

"Rassilon gave us express orders, and Rassilon had his reasons. He knew that for all their power, for all their knowledge, his Time Lords aren't perfect. He realised who the enemy really is."

When Omega returned to the universe, Raimor and Peltroc discussed his presence on the list of four names. According to the two Watchmen, the Doctor was also one of the four names, and was only to be killed following an unknown event or action. (PROSE: The Infinity Doctors)

Behind the scenes

 * In the non-narrative source AHistory, Lance Parkin implies that there is a connection between the Four Names and the four surviving elementals, but does not explicitly describe what the connection is but one of the names is The Doctor himself.