I go deeper than most. That's my thing — I'm one of maybe thirty people in GLMZ who regularly descend below B50, and one of maybe ten who've been below B60. I do it for the salvage, for the data, and because something pulls me down there that I can't fully explain. The deep levels are my cathedral. I know that sounds mystical. I don't mean it that way. I mean the scale, the silence, the feeling of standing in a place that humans built and then abandoned and that has become something else in their absence.

On January 28, I was at B60, Sector 2 — one of the deepest accessible points in the western Underworld. I was alone, which is stupid at that depth and I know it, but the deep levels are emptied out and I prefer solitude when I'm working. My headlamp was on its widest beam, throwing light maybe forty meters down a corridor that was three meters wide and showing signs of the biological growth you get at extreme depth — walls furred with mold, ceiling dripping with condensation, floor slick with something organic that I've never been able to identify.

At the edge of my light, standing perfectly still in the center of the corridor, was a figure. Bipedal. Upright. Approximately two meters tall. My first thought was that it was another explorer, but the silhouette was wrong. The proportions were wrong. The arms were too long — they reached past the knees. The head was too large, or rather too wide — broader than the shoulders, as if the skull had expanded laterally. And it had no light source. Nothing. It was standing at B60 in absolute darkness without any illumination, which means it either navigates without sight or it sees in spectra I don't.

We stood there looking at each other — or rather, I stood there looking at it, and it stood there oriented toward me in a way that suggested it was aware of me. For approximately thirty seconds, neither of us moved. I could hear the Hum — at B60, you always hear the Hum, that deep vibration that comes from below — and I realized, or imagined, that the Hum had changed. Gotten louder. More rhythmic. As if my encounter with this figure was accompanied by a change in the Underworld's own background noise.

Then it raised one hand. Slowly. Palm toward me. The gesture was unmistakable. Universal. A greeting, or a warning, or a farewell. Then it turned and walked into the darkness. Its gait was fluid and silent. I pointed my light after it, but the corridor curved and it was gone.

I did not follow. I ascended immediately. I have been below B60 four times since. I have not seen the figure again, but I have found footprints — barefoot, humanoid, but with six toes on each foot — in the organic film that covers the corridor floors. The footprints were not there before January 28. I am not the only person who has seen something like this. I am merely the first willing to attach my real name to the account.