Exile: The Legend of Drizzt, Book II by R.A. Salvatore

Short profile:

As I became a creature of the empty tunnels, survival became easier and more difficult all at once. I gained in the physical skills and experience necessary to live on. I could defeat almost anything that wandered into my chosen domain. It did not take me long, however, to discover one nemesis that I could neither defeat nor flee. It followed me wherever I went–indeed, the farther I ran, the more it closed in around me. My enemy was solitude, the interminable, incessant silence of hushed corridors.

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