All about her, as suddenly as the awakening from a dream, the nothingness had opened out into undreamed-of… — C.L. Moore

And not until then did she remember how fatal it is said to be to accept a gift from a demon. Buy, or earn it, but never accept the gift.

She half expected, despite her brave words, to come out upon the storied and familiar red-hot pave of hell, and this pleasant, starlit land surprised her and made her wary. The things that built the tunnel could not have been human. She had no right to expect men here. She was a little stunned by finding open sky so far underground, though she was intelligent enough to realize that however she had come, she was not underground now. No cavity in the earth could contain this starry sky.

It was a long way down. Before she had gone very far the curious dizziness she had known before came over her again, a dizziness not entirely induced by the spirals she whirled around, but a deeper, atomic unsteadiness as if not only she but also the substances around her were shifting. There was something queer about the angles of those curves. She was no scholar in geometry or aught else, but she felt intuitively that the bend and slant of the way she went were somehow outside any other angles or bends she had ever known. They led into the unknown and the dark, but it seemed to her obscurely that they led into deeper darkness and mystery than the merely physical, as if, though she could not put it clearly even into thoughts, the peculiar and exact lines of the tunnel had been carefully angled to lead through poly-dimensional space as well as through the underground—perhaps through time, too.