Complex sentence: Mario, Timpani and company open a door of the final dimension to Castle Bleck, where they fight and defeat O'Chunks and Mimi, losing contact with Bowser and Peach in the process.
Split into simpler sentences: Mario, Timpani and company open a door of the final dimension to Castle Bleck. They fight and defeat O'Chunks and Mimi, losing contact with Bowser and Peach in the process.