Blame!, Vol. 3 by Tsutomu Nihei

A relentless loner named Killy presses deeper into a vast, nightmarish megastructure in search of a mythical gene that can reconnect humanity to the Net, joined by a rogue cyborg scientist whose experiments both aid and complicate their quest; together they face murderous Safeguard sentries, bizarre silicon-based lifeforms and desperate, decaying human enclaves, battling through collapsing sectors and uncovering grim hints about the city’s self-replicating systems and the tragic survivors clinging to fragments of civilization.

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