This archive tracks four layers. A record present in 2 of them (M41, 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
aeldari
The Aeldari library of forbidden lore, in the webway
The eldar repository of forbidden knowledge, often called a dark craftworld: a wraithbone labyrinth inside the labyrinth of the webway, behind a psychic barrier that turns away the weak and the corruptible. Few know it exists. Harlequins guard its passages, Guardian-Scribes its entrance, and the White Seers keep its records. Ahriman has sought a way in for nearly ten thousand years; in 998.M41, before the Thirteenth Black Crusade, he led his warband into the webway after it and came within sight of it before he was driven back.
Era Indomituspost-Rift
aeldari
The Aeldari library of forbidden lore, wounded by the Rift
Even hidden in the webway it was not spared the Great Rift: a section of the Library fell wholly into the warp, into the clutches of Slaanesh, and is tainted beyond the White Seers' power to cleanse. The last echoes of it in realspace were traced after the Rift to the western fringe of the Ghoul Stars.
Position
This record has no real-space position and is not placed on the map. The reason is in the provenance below.
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/Black_Library_of_Chaos (read directly in a browser on 2026-10-03): 'the Eldar's repository of forbidden lore'; 'The passages to the Black Library are guarded by Harlequins' and 'often described as a "Dark Craftworld"', 'a labyrinth within a labyrinth' (both citing Ahriman: Undying, Prologue); 'Ahriman of the Thousand Sons has sought entrance to the Library for nearly ten thousand years' (Ahriman: Undying, Prologue); the 998.M41 webway assault. https://wh40k.lexicanum.com/wiki/Masque_of_the_Falling_Moon: 'a Harlequin Masque which has devoted itself to guarding the Black Library of Chaos' (Undying, Prologue). NAME-COLLISION CHECK: 'Black Library' is also the publisher's name, so the label uses Lexicanum's full title and the short form is an alias only. No index record uses the id or label.
offMaphigh
unplaceable: 'the Black Library exists wholly within the Webway within the Warp' (Lexicanum Black_Library_of_Chaos). The post-Rift realspace echoes near the Ghoul Stars are traces, not the Library, so no gpos is given.
typemedium
editorial: a wraithbone artificial world inside the webway is modelled as a station with offMap set, as Commorragh is. No system survey (no-system-survey).
erashigh
m41 from the 998.M41 assault and the Ahriman: Undying prologue; indomitus from Lexicanum Black_Library_of_Chaos: 'Even hidden in the Webway the Black Library was not immune to the turmoil caused by the Great Rift, which caused a section of the Library to fall into the Warp completely' and the realspace traces 'within a triangle formed by the Exodite worlds of Syph and Quilan and ... Baal'. Allegiance 'aeldari'.