Complex sentence: The initial and most important conquest was of Pieria and the Bottiaei, including the locations of Pydna and Dium followed by a second stage which consolidated rule in Pieria and Bottiaea, captured Methone and Pella, and extended rule over Eordaea and Almopia.
Split into simpler sentences: The initial and most important conquest was of Pieria and the Bottiaei, including the locations of Pydna and Dium. The second stage consolidated rule in Pieria and Bottiaea, captured Methone and Pella, and extended rule over Eordaea and Almopia.