I have seen three.
They are real.
I do not know what they are.
Their existence does not "fit" into my Catholic belief system about what happens to the souls of the dead.
Whatever they are, we are not going to figure it out.
And if you think that it would be "cool" to see one and that you'd learn something from it. You are wrong.
It is terrifying, you learn nothing, and if you go looking for that sort of trouble, there is no reason to believe that the forces of good that normally keep those things at bay - whatever THEY are - guardian angels, perhaps? - are going to be at your beck and call because you go trafficking in spirits.
I think that if you bump into one of these things accidentally, it probably can't hurt you because the angels won't LET it.
I think if you go LOOKING for it, you are out of your freaking mind.
I also believe. My husband and I built our house when we were early 20's and then had our first child. When she was 14 months old she died in her sleep of SIDS. immediately after we both started hearing things. Neither of us said anything to the other for fear of being thought crazy but eventually we couldn't keep it to ourselves and told each other what we had each heard.
finally we left the house late one night after something grabbed my foot while we were in bed.
we still live there today. I don't hear anything anymore but my husband has had strange things happen when he is home alone, such as the windows being closed after he opened them, etc.
I don't know what it was but I know it scares you STIFF!! It is not cool or interesting, it is terror.