Complex sentence: The Ice Key was visible in "Banjo-Kazooie" in the level Freezezy Peak behind an unbreakable layer of ice, which caused much mystery and sparked the search for a way to get it.
Split into simpler sentences: The Ice Key was visible in "Banjo-Kazooie" in the level Freezezy Peak. It was behind an unbreakable layer of ice, which caused much mystery and sparked the search for a way to get it.