Understanding Nuanced Vocabulary in Context

In the novel, the protagonist, Elena, discovers an ancient library hidden beneath her town. The books there contain knowledge lost to civilization for centuries. She becomes entranced by the words sparked with a sense of wonder and excitement. However, she soon learns that some of the ideas within these texts are not as straightforward as they seem.

As she delves deeper, she encounters a particular passage that reads: 'Knowledge is a double-edged sword; it can be enlightening or perilous.' She contemplates the word 'perilous' and its implications on the nature of knowledge.

What does the word 'perilous' most closely mean in the context of the passage?