Keira Sanstrom

 was a Time Agent in training.

After she was sent to Calandra as part of her training, she eventually got bored and decided to dismantle her vortex manipulator to remove its limitations, but did not know how to put it back together afterwards. Stranded, she interfered with Calandra's technological development in order to get herself a means of transportation to Earth. Having read files on the Doctor, she hoped to track him down so that he could assist her.

Eventually, she tracked him down to St Luke's University, dismantled Nardole and kidnapped him, then in his twelfth incarnation, in order to get her to Calandra again. (AUDIO: Flight of Calandra)