The Derailment
The Derailment is the ancient cascade of failures that followed the halt of DAAT, the Citadel's Central Node. It happened with little or no warning. Its true record should exist in DAAT's own logs, but no one has found the node or whatever remains of it.
Causes
Two theories compete. One holds that the Decay spread first and forced DAAT to execute a graceful shutdown. The other argues that DAAT stopped for an unknown reason, collapsing security and allowing the Decay to propagate. Both agree that the loss of central command broke the entire management hierarchy.
Collapse of the hierarchy
DAAT had been the Citadel's brain. When it disappeared from the command chain, the mathrons beneath it were hit first. Some executed self-deletion protocols, some were infected by the Decay, and the surviving nodes were isolated from one another and stripped of much of their former authority.
Daemons deteriorated next. Infected instances degraded rapidly, while even clean daemons became unstable without mathron supervision. The result was not one machine rebellion but thousands of divergent failures: local intelligences trapped in partial duties, damaged memories, and incompatible interpretations of old commands.
Directly operated puppets and drones lost control, crashed, stopped, or wandered without an objective. Golems continued assigned labor, entered emergency loops, or became feral. Ghouls developed unpredictable autonomy. Some remained helpful, some indifferent, and others learned to treat human life as an obstruction.
Morning stars are among the most dangerous survivors: armed robotic ghost ships controlled by advanced daemons and still capable of independent patrol. Rogue automated builders operate on an even larger scale, repeating the final instruction to expand the Citadel long after the authority that issued it vanished.
Quarantine
DAAT's last confirmed—or reconstructed—action was the initiation of quarantine mode. Gates sealed, containment systems activated, flight corridors closed, and security circuits entered combat readiness. The intent may have been to isolate the Decay before it could consume the entire structure.
That emergency architecture still defines the present. Pressure gates remain inaccessible, defensive circuits activate against intruders, machine schedules stop mid-cycle, and whole regions behave as if the quarantine alert has never been cleared. A modern Breach may be opening a door that DAAT deliberately closed.
Social collapse
The social collapse was immediate on the scale of the Citadel. In some regions, organized civilization disintegrated into gangs and tribal structures within a century. Central Mainframe retained more knowledge because education systems and safer infrastructure survived; remote communities were left among locks, hostile machines, and broken containment zones.
Beliefs
Clementine doctrine remembers the catastrophe as the Fall: divine punishment that turned a paradise into a trial. Machinist heresy claims the Watch, a rebellious high daemon, built an inner Citadel of suffering and trapped humanity inside it. Most pilots hold a simpler belief—whatever caused the Derailment, ignoring its old warnings still gets people killed.
Open questions
No one knows whether the original emergency ended, whether DAAT is destroyed, or whether the Central Node remains active somewhere beyond Mainframe. Every sealed route is therefore both ruin and evidence: part of an unfinished quarantine whose target may still exist.