The Other Gods by H. P. Lovecraft

An aging, celebrated sage becomes obsessed with glimpsing the hidden, ancient deities said to dwell atop a remote, storm-wracked mountain; despite warnings from his young disciple, he leads an ascent to the forbidden summit, where curiosity and pride bring him face-to-face with forces beyond human ken and lead to a grim, supernatural reckoning that leaves only the disciple to flee and tell a cautionary tale about mortal hubris in the face of cosmic powers.

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