Void-Glass is a proprietary construction material manufactured exclusively on Xylos. It is a byproduct of refining Chronosite ore. When the ore is stripped of its temporal properties, the remaining silica sludge is superheated to create a transparent, incredibly dense material.
The defining property of Void-Glass is its acoustic dampening capability. A pane of Void-Glass only 1cm thick can block 120 decibels of sound. This makes it essential for construction in cities like Echo-Point, where the noise from The Whispering Skies would otherwise drive the population mad.
However, Void-Glass is brittle when subjected to sudden temperature changes. It is also extremely heavy, requiring reinforced frames. Because of its cost, the poorer districts of Xylos often use inferior "Sound-Crete," which only muffles the noise rather than blocking it completely.
Wealthy off-worlders import Void-Glass to build silent meditation chambers, treating it as a luxury good.