Shortly after arriving to Grensvayl and crossing the blazing perimeter, the Battle-Brothers noticed a breached (and previously well hidden) cave located into the western cliffs.
Deciding to investigate such location, they entered cautiously and came upon three paths.
To the south, they found some make shift living quarters with overturned cots and a scattered pile of broken cogs (all literally stained with old blood).
The cogs arrangement suggested the echo of the grotesque machine they once formed, leaving little doubt that the chamber was better off in its damaged state.
Several of the ruined components were etched with the symbol of a cog inside an eight-pointed Chaos star.
A mix on blood and oil in the floor suggested that bodies had been dragged away but a very mechanized body had been left behind. After taking a moment in order to recognize the pile of tubes, coils and manipulators, the Battle-Brothers realized that it had once been a living being.
The Kill-Team then made way to the chamber in the north to which they quickly faced themselves with a large, plasteel cylinder siting among debris and covered in a thick layer of grime. Lifeless bio-monitoring screens were checkering the stasis tube and a six-shackled adamantite restraint harness lied beside it.
While the other contents were largely empty crate and broken tools, a stack of parchment schematics and drained data-slated were found by the Battle-Brothers.
Among these schematics, the Kill-Team found one durable parchment filled with rick inks that had survived the years of dirt and dankness well. This was obviously an important document scribed with care and its main diagram showed an octagonal crystal conduit of indeterminate size. Several notations and sub-diagrams detailed runes and complex circuit patterns illuminated on the device.
Brother Azazel then proceeded to use his Psyniscience powers to exact that the aforementioned runes were indeed the markings of foul sorcery.
Finally, the Kill-Team proceeded to the last and widest chamber. This chamber seemed to had been prepared as to sustain a mining operation; the floor was embedded with metal squares as to even out the floor, dormant drilling lasers, extraction bits and complex storage arrays lined the walls of the large room ahead.
A huge central drilling column occupied the heart of the chamber and it was at that moment that the Kill-Team was ambushed by infected Aurans that were lying in cover behind such machinery.
Joining a couple of power cables that clearly sprung an elaborate trap, the infected Aurans activated the Decavane crystals lining the walls and suddenly jolts of energy were flying towards the Adeptus Astartes.
Taking some hits and dodging others, the Kill-Team managed to kill the enemies and inspect the mining operation closely. The Decavane crystals were indeed linked to directional electrodes (thus weaponizing them) but other than that, they didn't appear to power anything else. Other than that, numerous dull and grey crystals seemed to have been completely drained in this manner and remained in the floor, cold to the touch.
With the help of Brother Solomon via vox-link, a refining cylinder was identified to also be in the chamber, its sole purpose being bombarding the Decavane crystals with photons until they could be stable enough to be packed and transported.
Before leaving the cave, the Battle-Brothers also noticed a huge hole in the stone beneath the drill (several meters across and extending twenty meters down). The Battle-Brothers descended and saw an even larger hollow created by years of mining. Judging by the amount of rock removed and the density of the crystals still remaining in the walls, it was possible to verify that thousands of kilos of crystals may have been extracted.
The Battle-Brothers returned to the village of Grensvayl.