Final answer:
Santiago is describing the interconnectedness of events in his life and how they have led him on a journey.
Step-by-step explanation:
Santiago is talking about the interconnectedness of events in his life and how they have led him on a journey. This idea of a 'mysterious chain' refers to the idea that everything is connected and that each event in his life has a purpose or a reason behind it. For example, becoming a shepherd led him to have a recurring dream, which then led him to a city near Africa and ultimately to meet a crystal merchant. This concept of interconnectedness is a theme throughout the novel 'The Alchemist' by Paulo Coel.