Talk about it here.
Danna was a tutor at the Time Lord Academy and mentored a number of soldiers and diplomats including Irving Braxiatel, who was always late for class and once overshot the Delta Pools by a century. She taught him how to shoot down a flock of Pazithi bats with one shot whilst blindfolded and once walked him through a minefield in the Plains of Carthac to take refuge in the Forest of the Few, not telling him about the explosives. They were once besieged on Capra for three months. (AUDIO: Soldier Obscura)
Having met the Blind Soldier and learnt of the Last Great Time War, Braxiatel stationed Danna on a Time Lord research station which had been pulled into the threshold of the Obscura and told her that she was defending a weapon. In truth, he planned to keep her there to make use of her shooting abilities to take down a Dalek fleet in the war. Danna was left on her own, but received occasional visits from Braxiatel and was gifted enough books to make a makeshift library in one of the laboratories.
Danna began to grow old and tried to keep her hands steady by painting landscapes on the station's shutters, namely ones of Earth and Venus prior to its fall. She allowed the broken Daleks that wandered into nearby space to be pulled onto the station to remind her that there was an outside world and, during the twelve years that Braxiatel failed to visit her, she the Daleks began to look different, having wings attached to their casing.
One Dalek managed to survive getting to the Obscura but was driven mad by having looked at the Obscura. Shortly afterwards, Braxiatel returned to the station with Ace and prepared to defend the station when a Dalek fleet approached. Both of them noticed Danna's shaking hands and she proved unable to shoot a Dalek from only ten paces away. (AUDIO: Soldier Obscura)
Braxiatel realised how old and withered Danna had become and that she was useless to his plans. He gave her a military execution, which she accepted although it was not the way that she wanted to go. As a ghost of Obscura energy, she was able to save Braxiatel and Ace from a squadron of Daleks before the station was destroyed and she ceased to exist. (AUDIO: Soldier Obscura)