Mirror Mimicry – The character is a mirror.
The Magic Mirror can answer most questions but not all questions (Fables V1 #19).
Martyn who is the last member of the Cult of Cold Flame doesn’t like what his mirror advises and reacts violently (The Books of Magic V2 #6).
The DC Silver Age liked to transform superheroes into mirrors or characters with mirror like qualities. I deal with the topic of DC Silver Age transformations in detail at DC Heroes Transformed! Part II Transformations Organized by Type.
Justice League of American V1 #7
Flash V1 #126
World’s Finest V1 #121
There are many mirrors in Trading Card Games.
Mirror of Erised
Mirror of Lacef