Complex sentence: As the story concludes, Wilmarth discloses the discovery from which he fled in terror: the discarded facsimiles of a face and hands, utilized by something inhuman to disguise itself as a man.
Split into simpler sentences: As the story concludes, Wilmarth discloses the discovery from which he fled in terror: the discarded facsimiles of a face and hands. These were utilized by something inhuman to disguise itself as a man.