The Man in Green

Thanks to the power of Sabine's referrals, not only did guild commissions pour in, but organizations lingering on the Merchant Guild's fringes also came knocking.

Members of the Cabbage Mission, for example, were sneaking around the Gloomy Depths.

While simultaneously denying their notorious reputation in the outside world, these green-clad weirdos began building some sort of detector with crude tools. They claimed they wanted to find Bapharian Ruins buried deep underground and repeatedly insisted that their intentions were legitimate, in the name of "archaeology" and "academic research".

However, the construction of their device was incredibly simplistic—
Tossing aside the delicate mechanisms of an Oculoid, they extracted the large metal tube from within, grandly naming it a "Resonance Cavity Tube". Next, they tied a red crystal-like rubbing with a metal wire and hung it inside the tube.
With that, the detector for locating Bapharian Ruins was complete.

According to the green-clad weirdos, its working principle was as follows:
Place the detector in an open area. If Bapharian Ruins are buried there, the hanging rubbing is attracted by the underground energy, and sways inside the tube, striking the walls to produce a muffled sound. This indicates something below; the more frequent and rapid the sounds, the larger the ruins.

As for whether this principle is credible... that's another matter altogether. However, that rubbing hanging on the metal wire was all too familiar.
It is nothing other than Crimson Marrow, full of Xeno Engrams.