Factories of Crystal (called "Foces" for short) are the primary form of transport for the Firmament, and are given to members of the Firmament upon graduation from school. Foces are moon-sized vessels of blue-white crystal with a glowing light in their center, and a control tower on their surface. While the control tower is where the operations of the ship are centered, it is still the size of a large moon with all of the surface area that entails. Foces can have huge structures on their surfaces, and hold large numbers of beings. Crystal Titans perform much of the upkeep on the ships.
Every Foce is controlled by a Pilot, a mortal being (usually human) pulled out of time before their death, and plugged into the Foce's systems to run it as a living navigation system.
Factories of Crystal gain their name from their ability to produce the crystal dust that facilitates most inter-universal travel.
One alternate Graelyn Scythes was one of, if not the only, non-firmament to have a Factory of Crystal after that incident.
Lady Aesculapius is one of the most notable travelers in her own Factory of Crystal.