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
imperium
Imperial world in the path of a Tyranid hive ship
An Imperial world, otherwise unrecorded, whose population is threatened late in M41 by an approaching Tyranid hive ship; an Ultramarines strike force arrives to destroy the hive ship before it can reach the world (Catechism of Hate, Prologue).
Era Indomituspost-Rift
[RECORD LOST]
No record for this location in Era Indomitus.
Position
Map frame: 899.7, 700 in the archive's 0–1000 disk space (core at 500, 500).
Distance from the core: 447 units ≈ 47.6k light years, south-east of the galactic core.
Height above the disk plane: -7.3 units — invented thin-disk jitter, deterministic per record. No published source gives any location a z coordinate.
System: Argo Secundus System
Books set here
1 title in the reading tracker touches this record. 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/Argo_Secundus (read directly in a browser with fetch-page.mjs, 2026-10-05): 'Argo Secundus is an Imperium world that has been recently been threatened with the appearance of an approaching Tyranid Hive Ship. Luckily for Argo Secundus' population, a strike force from the Ultramarines Chapter has now arrived to destroy the Hive Ship, before it reaches the world.' Infobox Affiliation: Imperium; Segmentum, Sector, Subsector, System, Population and Class all 'Unknown'. Sole source: Catechism of Hate (Novella), Prologue. NAME-COLLISION CHECK: no index record uses the id, the label or 'Argo'.
book-joinmedium
VISITED for Catechism of Hate: the Prologue is set in its approaches, as the Ultramarines strike force arrives to destroy the hive ship (Lexicanum Argo_Secundus). Whether the world itself is seen on the page is not stated.
segmentumhigh
null, stated rather than guessed: Lexicanum's infobox gives Segmentum, Sector, Subsector and System as 'Unknown', and no other page read gives a bearing.
classlow
'temperate', with no look words to go on: Lexicanum's Class is 'Unknown'. The neutral settled-world ramp asserts nothing about terrain; revisit if a source describes the world.
gposlow
inferred: named in the novella's Prologue (Lexicanum Argo_Secundus) and unplaced anywhere, with no segmentum, sector, subsector, bearing or theatre published. Unsurveyed rim (rim_xy('argo-secundus') = [899.7, 700.0], r = 447.0 of the 470-unit disk, outside every stylised segmentum polygon; the function evaluated on its own, reproducing sturndrang exactly; build_locations.py not run), no positional information. Z -7.3 is the zPolicy value (compute-z.mjs argo-secundus 899.7 700).
erasmedium
m41 only, the era of its one source (the novella is set late in M41, after Ichar IV). Allegiance 'imperium'.
systemIdlow
'argo-secundus', named for the world because no system is published (Lexicanum: System 'Unknown'). 'Secundus' implies an Argo system with at least one other world that no page names.
no-system-surveyhigh
No systems/argo-secundus.json: a world of the Prologue, and canon names no star, sibling body or body count. The map synthesises its globe from this record.