A generation ago, a black disc settled into the air over the city of Arad. From what corner or quadrant of space it had come, no one knew. Before the afternoon was out, steel cables would descend in vast numbers from the disc, guided and attached by black metal spiders who struck dead any humans who dared intrude on their labors. Some fled, some prepared to fight, some hid, but within twenty four hours the city was entombed in blackness, behind walls of steel cables so thick in most places that they would never be broken.
The people of Arad gathered to resist, and while most were frightened, a few fought. They sought to cut out through the cabeline walls, but the metal spiders came once more to defend the barriers. For weeks and months war was fought, but the spiders seemed unending, and they were hard to kill, and the few humans who were willing to struggle were quickly brought down. In a short time, there were none left who would resist.
Little changed under the web. Electricity was made and food was grown under the brightest of lights; some guilds, houses and orders grew strong and some faded; and a generation grew up in the dark.
Now some of those children of the dome wish to be free, to see the sun, to travel the worlds. They wish all the world to be theirs, and they do not recall the deaths of those who fought. So they are brave, and foolish, and perhaps they will succeed.