The oppressive darkness pulsed with a life of its own. It wasn't simply the absence of light; it was a presence, a suffocating weight that pressed against their chests, a palpable entity teeming with unseen horrors. The silence, broken only by the occasional drip of water from unseen sources, was far more terrifying than any shriek or roar. It hinted at the lurking, the watching, the things that moved just beyond the edge of perception. Then, the first sign: a flicker of movement in the periphery, a shifting shadow that resolved itself into a creature of nightmare.