It sounds a bit like [Jonathan Strange & Mr Norrell][1]

It follows the two title characters who are initially working together but later feud. There is some time given to trying to track/capture fairies.

[Wiki][2] mentions a character using a mirror to move between locations in the 3rd act/part

Jonathon Strange definitely sees candles burning inside people's heads as he goes a bit insane towards the end.

> “May I ask you something?" Dr Greysteel nodded."Are you not afraid that 
> it will go out?"
>
>"What will go out?" asked Dr Greysteel.
>
>"The candle," Strange gestured to Dr Greysteel's forehead. "The candle inside your head.”

(quote from https://www.goodreads.com/work/quotes/3921305-jonathan-strange-mr-norrell?page=2)


  [1]: https://www.goodreads.com/book/show/14201.Jonathan_Strange_Mr_Norrell
  [2]: https://en.wikipedia.org/wiki/Jonathan_Strange_%26_Mr_Norrell#Volume_III:_John_Uskglass