|Ice World/Mining World/Tomb World
Simia Orichalcae is an Ice World of the Imperium, uninhabited except for Promethium processing plants scattered across the planet to refine deep underground veins of rare ice into usable promethium.
The origins of the planet's name remains unknown. After some research, the most plausible theory that Inquisitor Amberley Vail could produce was that, it refers to a statue or effigy in a past epoch, but the importance of commemorating the genus Simia remains unknown.[1a]
It is, however, most notably featured as the planet where Commissar Ciaphas Cain along with the Valhallan 597th were deployed to defend a promethium refinery against marauding bands of Orks[1b], and later encountering Necrons released from stasis by the presence of sentient life.[1c] It was later speculated that high-ranking Magi of the Adeptus Mechanicus, had deliberately built the refinery above the Necron Tomb, in order to investigate it.[1d]
Commissar Cain attempted to destroy the Necron Tomb, along with a Necron Dolmen Gate, with melta bombs, but initially failed.[1e] In desperation, he filled the deep underground caverns beneath the processing plant with promethium from a reserve, with the help of Magos Logash, and "got the frak out of there". [1f]
The Imperial Guard, realizing that they could not defeat an endless wave of foes (noting that said foes were apparently indestructible without the help of an Astartes Chapter), on top of a wave of Orks being led by a Gargant, promptly chose to evacuate the mining colonies to an awaiting ship, the Pure of Heart.[1g]
From there, they detonated the promethium-filled caverns with bombs placed by sappers originally meant for the approaching Gargant. The blast was so powerful that shockwaves were felt throughout the already-spaceborne Pure of Heart, and left a kilometers-wide crater that permanently scarred the pristine icy-beauty of Simia Orichalcae.[1h]
Inquisitor Vail later launched an investigation and, much to everybody's relief, found no evidence of any further Necron activity; although she privately admitted that she was none too keen to be the first to start digging holes to find out for sure.[1i]
Simia Orichalcae is Latin for "Brass Monkey". The expression "cold enough to freeze the [blank] off a brass monkey" is a common colloquialism in M2.
- 1: Caves of Ice (Novel) — Ciaphas Cain: Hero of the Imperium (Omnibus)