Every human must have a "Shadow Dream"?

My friend said that before any human can die, they must have a "Shadow Dream". The Shadow Dream is when you dream about black figures and when you open your eyes they are still there, after about five minutes they will leave (disappear). She says that they don't do anything to you or anything to you but that they do stand there for about five minutes. I've never had this dream and I'm really scared to having to experience this. On top of that, three other people said that they have had the dream to, when she started talking about it. So I'm not gullible, I just need to know, what the deal with this?