This archive tracks four layers. A record present in 1 of them (IND) 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
[RECORD LOST]
No record for this location in The 41st Millennium.
Era Indomituspost-Rift
contested
Imperial world under Tyranid invasion, ca. 012.M42
A sparsely populated Imperial world beside the Herodian warp gate, the link to the frontiers of Segmentum Obscurus, with an abandoned Adeptus Mechanicus base on its surface. About a century after the Badab War a Tyranid splinter fleet descends on it; the Mantis Warriors answer its distress call and evacuate some 270,000 people, and a Deathwatch kill-team under Captain Quirion Octavius and Inquisitor Kalypsia is sent down into the swarm (Warrior Brood).
Position
Map frame: 101.6, 709.2 in the archive's 0–1000 disk space (core at 500, 500).
Distance from the core: 450 units ≈ 47.9k light years, south-west of the galactic core.
Height above the disk plane: 5.5 units — invented thin-disk jitter, deterministic per record. No published source gives any location a z coordinate.
System: Herodian 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/Warrior_Brood_(Novel ) (read directly in a browser on 2026-10-03): Black Library's description, 'The world of Herodian IV is doomed when the nightmarish Tyranid Hive Fleets descend'. Corroborated, all citing the novel: https://wh40k.lexicanum.com/wiki/Mantis_Warriors ('Herodian IV: The Mantis Warriors answered a distress call from the planet when it came under Tyranid attack. They managed to evacuate 270,000 people', ch. 1); https://wh40k.lexicanum.com/wiki/Brutius_Parthon ('an abandoned Adeptus Mechanicus base on the sparsely populated planet Herodian IV', ch. 11; the Herodian warp gate, chs 6 and 11); https://wh40k.lexicanum.com/wiki/Quirion_Octavius; https://wh40k.lexicanum.com/wiki/Kalypsia; https://wh40k.lexicanum.com/wiki/M42 (ca. 012.M42, ch. 6 pg. 79 and Epilogue). NAME-COLLISION CHECK: Lexicanum's Herodian_IV page does not exist, and no index record uses the id or label.
book-joinhigh
PRIMARY for Warrior Brood (deathwatch::dw-goto::1): the whole novel is the Herodian IV mission, its two drops, the hidden base and the extraction (Black Library description; Lexicanum Quirion_Octavius, Broec chs 3-11, Brutius_Parthon).
segmentumhigh
No source read places it in a segmentum. Lexicanum Brutius_Parthon and Quirion_Octavius say only that the Herodian warp gate leads to 'the frontiers of Segmentum Obscurus' and that if the planet fell 'the link to the Segmentum Obscurus would fall as well', which makes the gate a route TO Obscurus and does not say which segmentum Herodian lies in. No segmentum is claimed.
classlow
editorial, NOT a citation: no permitted source describes what Herodian IV LOOKS like (terrain, climate or colour); it is a sparsely populated inhabited world with an abandoned Adeptus Mechanicus base. Rendered `temperate` as the neutral default for an inhabited world, as for Lentonia, Nikaea and Aldana. Not `dead`: the Exterminatus that ends the book is its final act (kept to the spoiler), and an era is drawn in the state most of its books are set in. Repaint if a permitted source describes its surface.
gposlow
inferred: no page read names a segmentum, sector, subsector, neighbour or bearing for Herodian IV beyond a warp gate that leads to the Obscurus frontier, so there is nothing to place it against. The record claims no segmentum and sits on the unsurveyed rim at the generator's rim_xy('herodian-iv') = (101.6, 709.2), reproduced from build_locations.py's own fnv1a/CORE (checked against Lentonia's stored point (64.3, 594.2); the generator was not run). The position carries no information and must not be read as one. Z 5.5 is the zPolicy value (compute-z.mjs herodian-iv 101.6 709.2).
erasmedium
indomitus only: Lexicanum M42 dates the Herodian IV campaign ca. 012.M42 (Warrior Brood ch. 6 pg. 79 and Epilogue), and List_of_Media_set_during_the_Era_Indomitus (Notes, Pre-2017 Media) places the novel in the Age of the Dark Imperium because ch. 6 sets it nearly a century after the Mantis Warriors were judged for the Badab War. Allegiance 'contested': an Imperial world with a Tyranid swarm on its surface. No source read says anything of it in hh, aoi or m41. The Exterminatus is kept off the record (spoiler).
systemIdhigh
herodian: Lexicanum Quirion_Octavius says the kill-team 'travelled to the Herodian system', and Brutius_Parthon names the Herodian warp gate. The system has a survey (systems/herodian.json, TRUNCATED).