Hi auxitrooper and welcome to SRI

I did have similar experience during a few Reiki healing sessions where I could "see" demons attached to persons back or in one case it even jumped on me.
It is very good you are sitting in meditation and calming your mind. I feel that meditation is a VERY important part of the reiki healing system.
I understand that it is much easier following guided meditations but sooner or later to be discarded and on is to face one self as one is

no one can guide you into a subtle world of your self

you must go there on your own, totally alone.
I suggest you start sitting with your own self to know your self to get to know your own mind, your conditioned you, observing your fears and anger, your desires and aversions.
How can you tell whether this "demon" was not only a fragment of your imagination, your monkey mind's imagination

It is easy going back into "seeing visions" but not that easy knowing one self. Try and sit in silence observing nothing more but one self as one is at that very moment in life.
I would suggest you Shamatha to start with;
Sit calming your body and brining mind attention to your whole body breathing (without focusing on anything otherwise you might end up self hypnotising ). As soon you see your mind becoming busy bring your attention to the whole body breathing back again, but gently and do not beat your self over not being able to keep calm mind for long periods of time. The mind will follow the relaxed body.
Fear comes only from not knowing one self :-) sit alone with your own self and leave those guided meditations aside (say thanks to them but do let go of them).
To inspire you on this journey I would recommend this short but fantastic read;
http://www.messagefrommasters.com/Ebooks/Jiddu-Krishnamurti-Books/Freedom_from_the_Known.pdfIf you need more help please ask :-)
Remain relaxed, RQ