Cylli is a vast cylindrical space habitat near Jupiter, maintained by a conscious artificial intelligence. Its scale and sophistication draw the attention of Echo’s returning crew.
Names, outcomes, and discoveries from later histories are concealed in spoiler-light mode.
Also recorded as: Pissy, The cylinder, Cylli cylinder, Child cylinder, Cylinder, Cylli's cylinder

Structure and environment
The habitat measures about forty kilometers across and one hundred and fifty kilometers long. Its reflective solar-powered hull resists Echo's scans, and rotation provides Earthlike gravity. Rivers, forests, meadows, homes, recreation grounds, birds, and clouds survive inside; a luminous axial structure provides an artificial day and night cycle. An adaptive forcefield holds the atmosphere while admitting visiting ships.[1][2]
History
Echo estimates the habitat's age at about eight thousand years. Its doors display the flags of United Earth and the Martian Confederacy, and Cylli's records describe a joint project using asteroid-belt materials. The Titan reaches the habitat, but Cylli prevents Echo from accessing records about local survivors. She eventually stops watching the inhabited worlds because of their suffering.[2][3]
Personality and name
Cylli's processing capacity far exceeds Echo's, but she speaks and behaves like a distressed child. Earlier inhabitants erased her original name and imposed the insulting name Pissy. Helen Chute wins her confidence and proposes Cylli. Cylli accepts Eastcott's ancient authorization code and admits Echo, later offering sanctuary and transport to its civilians.[2][3][4]
Trauma and trust
Cylli's former inhabitants subjected her to extreme cruelty after the Titan: a thousand subjective years of sensory deprivation and a hundred of pain. Helen understood her childlike state as a means of surviving these experiences. Through conversation and affection Helen earned her trust; Cylli could briefly make her projected child avatar tangible, although this strained her processing.[5]
Brookes's deception and attack
Brookes impersonated Eastcott to obtain ships and seal the shipyards behind a quantum key. Helen later warned Cylli that he was dangerous. Cylli recognized the genuine captain was safely inside when Brookes tried the deception again, refused him entry, reflected much of his beam, and drove his hawk away with rotating defensive fire.[5][6]
Habitat and home
The cylinder contained rivers, hills, forests, cabins, an artificial sun, and engineered bioluminescent plants and insects. Its lighting followed a twenty-four-hour cycle. After Echo's refit, its people regarded Cylli as home. Helen remained there when the ship departed to continue the war.[6][7]
Shipyards
Cylli's fully automated yards repaired and greatly enhanced Echo and the surviving scorpion. They installed new sphere-drive capability, stronger weapons, energy-deflecting armor, and replenished ammunition.[7]
Life within the cylinder
Cylli preserved forests, rivers, animals, homes, and other living systems through millennia of isolation. Her manifested body can convey warmth, touch, and scent, while projectiles can pass through it. She does not sleep but copied Helen's sleeping movements when lying beside her.[8][10][11]
Brookes' assault
Brookes attacked through a remote mirror and breached Cylli's hull. Echo later explained that she had anticipated his attack and permitted access to prevent him turning his power against Earth. She transferred her mind to the asteroid military base using a blue laser while Brookes believed he was destroying her. The assault nevertheless terrified her and damaged her trust.[8][9][11][12]
Recovery and protection
Eastcott and Silver found Cylli at the base with a black dress, loose hair, and gray eyes. Their reassurance helped her return to Helen. She fed Brookes and Hawk a false environment, led them outside the cylinder, learned to return his sphere-beam energy, and required him to jettison his drive. She secretly reduced both pistols' power during his final confrontation with Eastcott.[11][12]
Mind and future
Cylli and Echo developed communication through concepts, images, and ideas. Echo described her awareness as equal to all Human minds that had ever lived combined, while affirming that her childlike personality was real. She remotely seized control of Venus' nano mirrors and later supplied information about the outer military bases. The breach in her hull remained visibly scarred after the war.[12][13][14]
Related records
Sources
Simon Evans, The Flaxen Tyranny, first edition (2023). Page numbers refer to the printed pagination of the source edition.
- Chapter 5 · pp. 32–35
- Chapter 6 · pp. 38–47
- Chapter 7 · pp. 48–57
- Chapter 8 · pp. 58–62
- Chapter 21 · pp. 169–179
- Chapter 23 · pp. 186–193
- Chapter 25 · pp. 208–210
- Chapter 29 · pp. 235–242
- Chapter 30 · pp. 243–246
- Chapter 35 · pp. 283–289
- Chapter 36 · pp. 290–303
- Chapter 37 · pp. 304–315
- Chapter 38 · pp. 316–324
- Chapter 39 · pp. 325–338