I was sitting in a healing temple in a Spiritualist camp and a total stranger to me was getting a healing.  Impressed over his face was my father.  There is no doubt in my mind that is who was there for me.

Spirit entities can cause mischief.  But unless we give up all our consciousness...totally...which no one does....the spirit can not overtake us.  I have 'channelled' ...for want of a better word....a recently deceased, murdered, spirit.  It took some doing, but eventually he went to the light to be helped over.  

There is a book called 30 Years Among the Dead which is the entrancing of a medium to 'channel' the deceased spirit embeded in a patient of an asylum for them mentally ill.  Once removed, the patient came back to their normal consciousness.

This is not transfiguration!  In the manifestation of transfiguration, there is a substance (ectoplasm) that is placed as a mask over the medium and then spirit entities use it to present an image of themselves for all to see.