As a Time Lord
Eventually, Quarren realised the power he possessed, and when the Time War broke out, he turned himself into a human as he knew the Time Lords would want to use his power in the fighting, and believed they would abuse it when they had used it too often. (AUDIO: One Life)
The Chameleon Arch that Quarren used had created an entire life for him, even making it seem that he had been married to Rupa for 20 years, both of them completely convinced of this. In reality, the circuit, along with Quarren's powers, had made this up entirely. The Eighth Doctor estimated that they had only truly known each other for about a small number of years. (AUDIO: One Life)
Still unaware about his true identity, Quarren and Rupa were onboard the Theseus when it was attacked by Daleks. They became part of the Eighth Doctor's group of survivors and joined him on a Dalek ship, which crashed on a jungle planet soon after leaving, the Theseus following swiftly. (AUDIO: The Starship of Theseus)
He explored the jungle with his wife and watched it constantly grow and die. He became nervous when the Doctor got Dal, a damaged Dalek, to navigate them to a safe zone. He tried to convince his wife that the Time Lords were fighting the Time War for a reason. When he came in contact with The Doctor's TARDIS he noticed something familiar about it. (AUDIO: Echoes of War)
After the Daleks attempted to track him down, his identity was exposed by Ollistra while he was attempting to escape with various other human refugees in the TARDIS. Out of options, Maguire opened the Arch and restored himself to his original state, rewriting reality to save the TARDIS and send most of the human refugees to safety- although he left the Eighth Doctor with the company of his new acquaintance Bliss to act as his new companion- while sending the other Time Lords away from the TARDIS. This action also erased his entire human life from history, with the result that Rupa no longer had any memory of meeting him or their marriage.