Shrouds are massive zones of artificially restructured spacetime, built by the Shrouders to house and hide their civilization. The perimeter of a shroud is a roiling vortex of warped metric, which will destroy any object that approaches too close. However, Shrouders (or individuals who have been given Shrouder neural patterns, through the Pattern Jugglers) can pass through this region without harm.
Further into the Shroud is a region known as "revelation space," where the metric technology that generates the Shroud can interface directly with the minds of intelligent beings. Those who have made it this far into the Shroud report being imparted visions or knowledge by the Shrouders.