Complex sentence: Afterward, the game remains virtually open-ended, with the ultimate goal of the player being to obtain at least one member of each of the different species of Pokémon, thus completing the Pokédex.
Split into simpler sentences: Afterward, the game remains virtually open-ended. With the ultimate goal of the player being to obtain at least one member of each of the different species of Pokémon, thus completing the Pokédex.