Complex sentence: Upon finally managing to encounter Hyde, Utterson is amazed by how ugly the man seems, as if deformed; though Utterson cannot say exactly how or why, Hyde provokes an instinctive feeling of revulsion in him.
Split into simpler sentences: Upon finally managing to encounter Hyde, Hyde's ugliness, as if deformed, amazes Utterson. Although Utterson cannot say exactly how or why, Hyde provokes an instinctive feeling of revulsion in him.