The Fraction

On the eve of his near-triumph during the Canisian invasion, Tannis, who believed that he was nigh to become the last Time Lord standing, gleefully declared to Casmus that he had "disposed of the Time Lords of the Fraction". (WC: Death Comes to Time)

Notably, the Doctor and Casmus identified themselves as "god[s] of the Fourth". (WC: Death Comes to Time)

Behind the scenes
The term "the Fraction" occurs only once in Death Comes to Time. The significance and even the syntax of Tannis's line are ambiguous: "the Time Lords of the Fraction" could be another group listed in addition to, and separately from, the Saints Valentine and Antenor, the Doctor and the Minister, and Casmus; alternatively, "the Time Lords of the Fraction" might be comprised of the Time Lords named in the rest of the list, either because "the Fraction" is their informal name – perhaps in reference to the Fourth – or because "the Fraction" is the name of a location, possibly the reality of Death Comes to Time itself, which would make "the Time Lords of the Fraction" analogous to a phrase such as "the Time Lords of Gallifrey".