What does "spectremancer" mean?

I accidentally know this word while reading a manga in English. I tried searching it on the Internet but nothing comes out. Yet I found that maybe this word was originally "spectromancer" since there are no websites containing the word spectremancer All of the information about spectremancer is little:

"But there're others too, like that weird spectremancer."

I believe this word describes a type of person or an occupation.

[Source: MangaRock {Chapter 26, Page 8}]

Solution 1:

spectre: A ghost.

necromancer: A person who practises necromancy; a wizard or magician.

necromancy: The supposed practice of communicating with the dead, especially in order to predict the future.

necro-: Relating to a corpse or death.

-mancy: Divination by a specified means.

divination: The practice of seeking knowledge of the future or the unknown by supernatural means.

All can be found on https://en.oxforddictionaries.com/

Thus, by analogy, we have (I made this up):

spectremancer: A person who practises seeking knowledge of the future or the unknown by means of communication with a ghost.

Perhaps spectremancer is indeed a 'better' word than spectromancer, because spectro- represents spectrum (eg, spectrochemistry). However, people also use spectro- for ghosts:

Spectrophilia is sexual attraction to ghosts [...]