Ni is basically about... pretending to being in the future, and experiencing the sensations of being in that pretend-future-world. It's basically about separating yourself from the present-moment, and imagining yourself in different time periods.
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Ni synthesis ideas, connects multiple ideas together. Ni-egos are very good at writing and storytelling. With Ni+Fe, INFp best objective writers. Based on social constructs, Augusta herself said this was true too (I think?)
I don't think it tells the future, but it is very intuitive, intuitive introversion - so it's very self-reflective. I don't see Ni-egos 'giving' themselves up very much, sort of self-contained. Ni understands the likelihood of an events happening, so they will usually supervise the ESE in a way such as "Do you really need to do that? You're overdoing."