Straxus (The Light at the End)

Straxus was a Time Lord who acted as an agent for the Celestial Intervention Agency.

Biography
Straxus once worked for the Celestial Intervention Agency. Unbeknownst to the High Council, he was instructed to gather from the Vess weapons that would allow the Time Lords to defend themselves and defeat races that posed a threat to Gallifrey. The Decayed Master discovered this and, by threatening to inform the High Council, blackmailed Straxus and the CIA into letting him buy a conceptual bomb from the Vess.

The Master used the device to attack the Doctor's timeline, erasing the Doctor's TARDIS and consequently everything he had accomplished. Recognising that the loss of the Doctor from history was causing too much damage, Straxus captured the Sixth Doctor to ask for his help in defeating the Master. Eventually, he regretted his own actions and claimed he meant to report to the High Council. His TARDIS was destroyed by the Sixth Doctor by forcing and expanding its dimensional stabilisation field, in order to let the Doctor's other incarnations land in the pocket dimension of the Vess at the same time. Although the first three Doctors were only able to partially materialise, this was enough for the other Doctors to work out what the Master had done and undo his attack, essentially erasing the whole crisis from existence. (AUDIO: The Light at the End)