The Temple by H. P. Lovecraft

A recovered wartime log recounts a German submarine captain’s descent into obsession after an attack leaves his vessel disabled near a lonely stretch of sea; as supplies and morale dwindle he becomes fixated on a strange, primeval structure glimpsed below the waves, and his increasingly fevered entries describe dives, uncanny discoveries, and mounting terror as ancient, inhuman forces and memories of past violence erode the crew’s sanity, culminating in a final, catastrophic encounter with something older and more malevolent than war.

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