This archive tracks four layers. A record present in 1 of them (M41) is silent in the rest, and says so.
The Horus HeresyM30–M31
[RECORD LOST]
No record for this location in The Horus Heresy.
Age of the ImperiumM32–M40
[RECORD LOST]
No record for this location in Age of the Imperium.
The 41st Millenniumpre-Rift
chaos
Lost Forge World returned from the warp, held by the Dark Mechanicus
A Forge World of the Adeptus Mechanicus that vanished into the warp amid rumours of corruption and civil war, and a century later drops back into real space in the middle of the Borosis System, disrupting its planetary alignments. Its tech-priests have become the Dark Mechanicus: possessed machines prowl the manufactoria and datafortresses of its cities, and out in the acid wastes stands a titanworks. In 999.M41, during Abaddon's 13th Black Crusade, an Ordo Malleus fleet under Inquisitor Nyxos and an Adeptus Mechanicus explorator mission blockade it and send Justicar Alaric's Grey Knights down, while the Black Legion's Hellforger answers its call. Dark Adeptus is set here.
Era Indomituspost-Rift
[RECORD LOST]
No record for this location in Era Indomitus.
Position
Map frame: 710, 785 in the archive's 0–1000 disk space (core at 500, 500).
Distance from the core: 354 units ≈ 37.7k light years, south-east of the galactic core.
Height above the disk plane: 2.6 units — invented thin-disk jitter, deterministic per record. No published source gives any location a z coordinate.
System: Borosis System
Books set here
1 title in the reading tracker touches this record, 1 of them as a primary location. Titles link out to the tracker.
Every fact in this record, and where it came from. Editorial derivations say so.
identityhigh
wh40k.lexicanum.com/wiki/Chaeroneia (read directly in a browser on 2026-10-03): 'a Forge World of the Imperium' (citing Dark Adeptus, Prologue); infobox Segmentum 'Ultima Segmentum', Subsector 'Gaugamela Subsector', System 'Borosis System' (all citing Dark Adeptus, Chapter 3), Affiliation Imperium, Class Forge World. https://wh40k.lexicanum.com/wiki/Dark_Adeptus_(Novel): the publisher's description ('One hundred years ago, the forge world of Chaeroneia disappeared amidst rumours of corruption and civil war. Now it has returned ...') and summary ('come out of the warp in the middle of a new system, disrupting the planetary alignments'). https://wh40k.lexicanum.com/wiki/Alaric: 'an unknown planet that has suddenly appeared in the Borosis System in the Ultima Segmentum'. Lexicanum spells it both Chaeroneia and Chaeronia; the novel page, the world page and Alaric use Chaeroneia. NAME-COLLISION CHECK: Lexicanum full-text search for 'Chaeroneia' returns only this world and pages about this novel (Forge_World, Castigator_(STC), Alaric, Urkrathos, Hellforger, Saphentis, Feogrym); no index record uses the id or label.
book-joinhigh
PRIMARY for Dark Adeptus (grey-knights::gk-main::2.3): the whole novel after the orbital prologue is set on its surface: the crash landing, the city, the datafortress of Manufactorum Noctis, Antigonus's lair beneath it, the titanworks in the acid wastes and the Castigator (Lexicanum Alaric 'Chaeroneia' sections, Saphentis ch. 18, Antigonus, Castigator_(STC) ch. 7).
segmentummedium
wh40k.lexicanum.com/wiki/Chaeroneia infobox: 'Ultima Segmentum' (citing Dark Adeptus, Chapter 3), and Lexicanum Alaric: 'the Borosis System in the Ultima Segmentum'. The page is also filed under the category 'Segmentum Unknown', which its own cited infobox contradicts; the cited value is used.
classmedium
FORGE, medium. Painted from what the sources say it LOOKS like, not from the 'Forge World' tag alone: 'the once teeming factory planet' (the publisher's description), its cities, manufactoria and datafortress (Manufactorum Noctis, Lexicanum Saphentis), 'ancient data-engines' and an 'industrial complex' (Antigonus, Prologue), 'a large titanworks' in 'the acid wastes' and 'a Titan Field the size of a space port' (Alaric, Antigonus). An industrial, polluted, manufactory-covered world is what this dataset's forge palette draws. 'daemon' was refused: the corruption is of its priesthood and machines, and no source describes a warp-twisted surface; 'dead' was refused because the world is fully working, a century of production of Chaos Titans (Lexicanum Saphentis).
gposlow
inferred: segmentum-level. Ultima Segmentum is published and so are the Gaugamela Subsector and the Borosis System (Lexicanum Chaeroneia, ch. 3), but no sector is, and the index holds no Gaugamela or Borosis record to place against, so the marker sits in open Ultima space at [710, 785], inside the stylised 'ultima' polygon (104 units from its edge, checked) and 80 units from the nearest existing marker (Kallash), so it implies no neighbour. The position means only 'somewhere in Ultima'. Z 2.6 is the zPolicy value (compute-z.mjs chaeroneia 710 785).
erasmedium
m41 only: Lexicanum Standard_Template_Construct dates the Castigator's discovery on Chaeroneia to 999.M41 (citing Dark Adeptus ch. 15), and Lexicanum Nyxos, Urkrathos and 13th_Black_Crusade place the events in the 13th Black Crusade; the shelf files the book M41 — Pre-Great Rift. Allegiance 'chaos' because the world is held by the Dark Mechanicus throughout the book (Lexicanum Dark_Adeptus_(Novel), Alaric, Antigonus); its infobox's 'Imperium' is its formal affiliation. The world's earlier history (its loss a century before, and Antigonus's time in the warp, which the Antigonus page reckons in hundreds of years) is not given an era of its own. No permitted source speaks of it in hh, aoi or indomitus.
systemIdhigh
borosis-system: Lexicanum Chaeroneia's System field reads 'Borosis System' (ch. 3), which has no page of its own; Lexicanum full-text search for 'Borosis' returns only Alaric, Saphentis and Chaeroneia. systems/borosis-system.json is a one-body TRUNCATED survey, authored because this is Dark Adeptus's PRIMARY setting.