Complex sentence: Marshall goes to Cooper's sister Sydney because he was chased out of his house by Gravedigger, who wants Marshall to walk the Morpheus Road, the way of life and death, with him to find the Poleax.
Split into simpler sentences: Marshall goes to Cooper's sister (Sydney) because he was chased out of his house by Gravedigger. Gravedigger wants Marshall to walk the Morpheus Road, the way of life and death, with him to find the Poleax.