64 chapters, I've realized again

When suffering became a ubiquitous background noise, it no longer felt unbearable but turned into something monotonous and persistent. The heart-wrenching pain slowly subsided, replaced by a vague, dull, and somber sensation, as if a once brightly colored world had suddenly been engulfed by an unceasing plum rain.

Stagnant, moist, sultry, each breath mixed with dense fog. The fog, carrying an unpleasant sensation, penetrated the respiratory tract, slowly spreading and filling the lungs. Ybur felt like a metal tool rusting slowly in the rain, with rust stains trickling down in reddish-brown.

"Nihility."

A voice suddenly whispered by its ear, "Nihility."

...What does that mean?