dieseldick
During my first year of university, I experienced an extremely potent hallucination. I was alone in my bedroom, attempting to go to sleep and in a semi-waking state. Naturally, this had an extremely strong influence on my brain - but nothing stronger than what happens to most people when they are going to sleep. I have never partaken in recreational drugs of any kind, and I do not drink alcohol (and never have). The experience I'm describin, while potent, was nothing more than a waking nightmare.
The hallucination I experienced was of a man levitating in front of me. His eyes were perfect circles (not ovals) - about the size and shape of a one-pound coin. He wore a tweed jacket, and spoke to me with a voice that sounded like he was underwater. He asked me to move some furniture around (which I did), and then asked me to get on the floor. I then got down on my hands on knees, and began barking the word "sin" like a dog. I did not feel like I had any control over my own actions. Lower down the scale, I also regularly hallucinate people sitting on the end of my bed/standing nearby and speaking to me when I am in a semi-waking state. This is by no means uncommon.
Now, I could very easily call "going to sleep" a "trance state" (or some such rubbish) and claim that the people I can see are ghosts or spirits or demons. Indeed, you regularly hear of people (in fact I know several) who claim to be psychic or to have had supernatural experiences based on nothing more than very common hallucinations associated with sleep paralysis.
Now, this is nowhere near the same as near death experiences. Nothing like the same league. People who are close to death experience profound alterations to their brain chemistry - far, far stronger than what happens when people are going to sleep. Considering that people in the latter state are capable of generating such powerful false experiences, the kinds of experience people have when they are near death must be extremely potent. I am not surprised they find them life-changing.
This does not mean that what people who are near death perceive is real. It can be horrifying, beautiful, or profound, I'm sure. But this says absolutely nothing about how real the actual sensory experiences are. You cannot trust your senses to reliably give you information about the real world when you know your brain chemistry is experiencing extreme alteration.
That is why near death experiences are not valid evidence of Satan existing.