Meanings of fantastic nightmare in English

That question linked the dark, gruesome, fantastic nightmare on to actuality.

Rilla felt as if she were in some fantastic nightmare.

The whole series of events seemed a grossly fantastic nightmare, yet it frightened him.

She felt as though she were in some fantastic nightmare in which nothing was as it seemed.

The whole thing was a fantastic nightmare.

Yet occasionally could be seen limbs wildly tossing in fantastic nightmare gestures, accompanied by guttural cries, grunts, oaths.

And yet I saw them in a limitless stream-flopping ,hopping ,croaking ,bleating-surginginhumanlythrough the spectral moonlight in a grotesque, malignant saraband of fantastic nightmare.

Only in fantastic nightmares could any human beings but Danforth and me conceive such optical effects.