No one need ever have known what I say now.

But for you no one need have known I was the author of that book!

"The same right that brought you here: the need to know new things."

No one need know you had any more contact with her than the other girls who went there to learn.

"If you do give her your blood, no one need ever know."

Possibly, but had she been up front about it, no one need have known.

I asked, more out of curiosity than any real need to know.

And if it was done properly, no one need ever know.

No need to let a mortal, even a small one, know he could do something a god couldn't.

The person's need to know 'when and how' is sometimes overwhelming.