Kotris

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

Work for the CIA
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. 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)

In a new incarnation, Straxus was sent by the High Council to the Doctor's TARDIS. He ordered the Eighth Doctor to Lonsis in 2006 to retrieve Lucie Miller from a temporal blackspot. The Doctor agreed on the condition that Straxus fix his TARDIS. Straxus agreed and gave the Doctor a time ring for his mission. On the Doctor's return, Straxus told the Doctor why Lucie was originally taken out of her own time and sent to the Doctor. He then helped the Doctor defeat the Cybermen on Lonsis before returning to Gallifrey. (AUDIO: Human Resources)

Straxus was later sent by the Time Lords to take the Doctor back to Gallifrey, where he was to be quarantined with the rest of the Time Lords in order to prevent the resurrection of Morbius. (AUDIO: Sisters of the Flame) Straxus failed to find the Doctor in time and instead was captured by Cristophe Zarodnix and was forced to surrender his DNA in order to resurrect Morbius. Straxus was imprisoned for ten years while Morbius fed on Straxus' life energy whenever he became weak. The Doctor and Lucie came for Straxus and the Doctor sacrificed his life to save the universe from Morbius. Straxus' life energy was restored after the Time Lords corrected history. Straxus was taken back to Karn, where he offered to take Lucie home to Earth. (AUDIO: The Vengeance of Morbius)

War in Heaven
During the War in Heaven, Straxus' future self was stranded on Earth in 1888 after his Time Ring failed during a mission. He tried several plans to escape or gain the attention of his superiors, including manipulating Ludwig Cooray to create the God Machine in 1893, (AUDIO: The Adventure of the Diogenes Damsel, PROSE: A Gallery of Pigeons) founding Straxus Imperial to collect historical artefacts that shouldn't have been discovered until much later, and using an emergency setting to attract other Time Rings. This last plan eventually succeeded in summoning Bernice Summerfield to London, but her Time Ring was keyed to a specific genetic pattern so Straxus couldn't use it.

Straxus wasn't the only one trying to get the attention of a superior through ritual: his Cwej assistant Septimus was committing murders themed around the number seven, hoping for notice from a "Pale God". The Cwej stabbed Straxus, resulting in his regeneration, but and also drew the attention of Straxus' previous self. The younger Straxus extracted, imprisoned, and interrogated his aborted future counterpart. (AUDIO: The Adventure of the Diogenes Damsel)

CIA Coordinator and Kotris
Straxus eventually became Coordinator of the CIA. (AUDIO: The Death of Hope) His next incarnation became fed up with the morally questionable actions of himself and his people, and allied himself with the Dalek Time Controller. The Dalek Time Controller helped him rewrite his biodata to remove his Time Lord heritage, so that when they retroactively destroyed the Time Lords the new Straxus — now calling himself Kotris, an old family name of his — would survive. Kotris knew that as Straxus he had attempted to avoid regenerating, and sent a temporal drone to prevent Straxus killing himself. Kotris and the Time Controller planned to incubate "retro-genitor particles" in a human named Molly O'Sullivan. They sent Daleks after her and the Eighth Doctor, forcing them to spend time together and allowing the retro-genitor particles to latch onto the Doctor's Gallifreyan DNA. The particles were then intended to follow that DNA back through history, undoing not just the Doctor's life, but all of Gallifrey's past.

The younger Coordinator Straxus was instructed by the Lord President of Gallifrey to send the Doctor to France during World War I. Straxus later saved the Doctor and his new companion Molly from a group of Daleks. His TARDIS was attacked by the Daleks and he escaped back to Gallifrey. Straxus attempted to kill himself by throwing himself off a mountain on Srangor, where regeneration was impossible, but was stopped by his future self's temporal drone. Straxus modified the retro-genitor particles implanted in Molly to target the Daleks instead of the Time Lords, but in a confrontation with Kotris and the Dalek Time Controller, the Time Controller killed him. This meant he could never become Kotris, and the scheme was entirely undone. (AUDIO: The Great War, Fugitives, Tangled Web, X and the Daleks, The Death of Hope)

Behind the scenes

 * On the 12 July 2011 edition of The Big Finish Podcast, Nicholas Briggs revealed that the original actor hired to play Straxus had to be fired. When the original actor proved unsuitable for the role, Briggs quickly called someone he knew — Nickolas Grace — to take over. The crew became so enamoured of his performance on the audio story Human Resources that they wrote Straxus into The Vengeance of Morbius. Briggs went on to claim that this was the only time in Big Finish's Doctor Who production where an actor had to be fired for performance deficiencies.