Reflection
Dr Chin Lee told Kate Stewart that her mother said that evil did not like its own reflection. (AUDIO: Open the Box) This was indeed the case with the Mara. (TV: Kinda; AUDIO: The Cradle of the Snake)
By 2007, a poster in a classroom at Deffry Vale High School referenced, among other things, reflection. (TV: School Reunion)
The female Saturnyns hid themselves on Earth using perception filters. However, this technology did not hide their reflections. Since brains could not process the two conflicting pieces of information, they had no reflections in mirrors. (TV: The Vampires of Venice)
Soon after regenerating, the newly-born Second Doctor briefly saw his preceding incarnation in his reflection. (TV: The Power of the Daleks)