Psychic defense against mediums

Has anyone enounted a medium summons names of the dead that are quite accurate? Well, is their a psychic defense against these type of people? I feel they are somehow invading the mind.

So, you're saying that the dead are trying to invade?
Or, that a medium is attempting to be invasive?

In the case of the medium, i wouldn't know if tis would be effectual, but i use what i call flame energy against entities. I consider myself very close to the element flame, and even convert my aura (visualization) to flames, and manipulate it further. There are all kinds of manipulations to be done with flame, and i;ve found in my case this works intantly against entities.

I wouldn't know if it would work so well against a medium- but then again, instantaneous results do require some amount of strength, i would think- and then, the last time i was mentally bothered by a bad medium, i had let my guard down.

Oh- but then there are mirrors (then again these are mostly for astral invaders), and invisibility barriers. Maybe try those?
Again, visualization.