This archive tracks four layers. A record present in 4 of them (HH, AoI, M41, IND) is silent in the rest, and says so.
The Horus HeresyM30–M31
ork
Ullanor Prime — ork empire, then the Emperor's Triumph
[RECORD LOST]
In this era the world is Ullanor, seat of a vast ork empire; breaking it is the campaign that ends with Horus raised to Warmaster at the Triumph. No hive city has been built on it and none will be for fifteen hundred years — what is down there is jungle, ocean and greenskins. Its position in this era is [RECORD LOST] — no published source gives Ullanor's coordinates before it was moved.
Age of the ImperiumM32–M40
contested
Ullanor, then Armageddon
The Beast makes Ullanor his capital during the War of the Beast. The Mechanicum are recorded as destroying the world; in fact they teleported it bodily into the Armageddon System, and the name Ullanor left the record.
The 41st Millenniumpre-Rift
imperium
Hive world; four Armageddon Wars
Fifty-five billion souls in hive clusters between ash wastes and jungle. Fought over by daemon, ork and Imperium in turn — Hive Hades and Helsreach are bywords for the worst of it.
Era Indomituspost-Rift
imperiumImperium Sanctus
Hive world; still contested
Still Imperial and still burning. Ork pressure never lifted, and the Fourth War opened with wholesale theft of matter out of the system by ork teleporta.
Contested record
Identity: canon reveals Armageddon to be the relocated world of Ullanor. Its pre-M32 position is unrecorded, so the marker shows only its post-relocation home.
Position
Map frame: 330, 470 in the archive's 0–1000 disk space (core at 500, 500).
Distance from the core: 173 units ≈ 18.4k light years, west of the galactic core.
Height above the disk plane: 7.6 units — invented thin-disk jitter, deterministic per record. No published source gives any location a z coordinate.
System: Armageddon System
Books set here
10 titles in the reading tracker touch this record, 9 of them as a primary location. Titles link out to the tracker.
wh40k.lexicanum.com/wiki/Armageddon §Secret Origins — Armageddon was originally Ullanor, teleported into the Armageddon System by the Mechanicum after the War of the Beast; one id carries both names across eras
era-hh-classmedium
wh40k.lexicanum.com/wiki/Armageddon §Geography — the world's surface is 'the Fire Wastes surrounding the north pole, the Deadlands around the south pole and one large equatorial' landmass, the halves of which 'meet in a region dominated by a massive jungle', all 'separated by a world ocean'; §History records feral orks still 'plaguing the planet's equatorial jungles' long after the Second War. That is the same rock in every era — but the HIVES are not, and `hive` is a palette of industrial terracing and sodium night-light. Ullanor in M30 has no hive cities on it at all. The hh entry therefore carries an explicit class of `feral`, which is this palette set's jungle-over-shallow-ocean world, and the baseline `hive` stands from aoi onward, when the hives exist. Read rather than transcribed: no source states a class for Ullanor, so this is our reading of the geography passage, applied to the one era the hives had not been built
gposmedium
derived: Segmentum Solar, a warp-route nexus reachable from Terra (Lexicanum:Armageddon_System) — placed north-east of Terra inside the Solar block, south of Fenris to match the relative ordering of the two on Lexicanum's own Solar segmentum map