What is the effect of sibilance

This depends on the content of the quote. First think about what the quote is actually saying. Is it something threatening? Is it describing something beautiful, or something quiet? The repeated s sound interacts with the meaning of the words to create a texture that heightens what the quote is saying. For example if the writer was describing a quiet, moonlit night, the sibilance would create a sense of secrecy and hushed stillness. If the writer was describing a scene where someone was hiding from a threat, it would create a feeling of creeping tension like a chill running up your spine.