"Enough to illuminate the dark places." River pulled enough away to smile at Ianto, then. "We seem to be mutually necessary for survival. Species cannot live in the black." There was a difference between the empty nothing of space and the sort of blackness that Ianto had found himself in. In space, there was always the promise of life -- of stars -- burning gas giants spinning at millions of miles an hour around supermassive black holes.
But where Ianto had been, there was -- nothing. There was only complete sensory deprivation. And the sensation that something was watching you...waiting. River looked away, a throaty whimper escaping from behind closed lips.