Sentence:  Our ancestors, who were forest dwellers, bequeathed us a legacy of wonder tales in which forests have a significant role ... One route would start from a refuge in a clearing. The path would set forth in a bright and optimistic manner. Difficult choices would appear. Divergent paths would become stony, enter dark woods and descend through <WSD>sloughs of despond</WSD>. 
Meaning of the word marked with <WSD> tags:  A dreary bog or marsh.