This archive tracks four layers. A record present in 2 of them (HH, M41) is silent in the rest, and says so.
The Horus HeresyM30–M31
imperium
Knight world; the Emperor's hidden warp gate
A fortified knight world the Emperor walked in person, because a gate into the warp was buried on it. Horus took the world apart to reach that gate and came back from the other side changed.
Age of the ImperiumM32–M40
[RECORD LOST]
No record for this location in Age of the Imperium.
The 41st Millenniumpre-Rift
unknown
[RECORD LOST]
[RECORD LOST]
we found no published record of Molech's condition after the Heresy.
Era Indomituspost-Rift
[RECORD LOST]
No record for this location in Era Indomitus.
Contested record
Segmentum: Ultima per the Lexicanum infobox; Lexicanum's own Segmentum Solar world list also names Molech.
Position
Map frame: 566, 398 in the archive's 0–1000 disk space (core at 500, 500).
Distance from the core: 121 units ≈ 12.9k light years, north-east of the galactic core.
Height above the disk plane: -6.5 units — invented thin-disk jitter, deterministic per record. No published source gives any location a z coordinate.
System: Molech System
Books set here
2 titles in the reading tracker touch 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.
segmentummedium
wh40k.lexicanum.com/wiki/Molech infobox Segmentum = Ultima Segmentum; but https://wh40k.lexicanum.com/wiki/Segmentum_Solar also lists Molech among its notable planets
derived: placed on the Ultima side of the Solar/Ultima border, north of the galactic core — the disputed segmentum reading is itself the strongest positional evidence available