Complex sentence: This led to a Handicap Casket match between Undertaker and Orton and his father at No Mercy, where Orton and his father defeated Undertaker, and set the casket, which Orton locked Undertaker in, on fire.
Split into simpler sentences: This led to a Handicap Casket match between Undertaker and Orton and his father at No Mercy. At the event, Orton and his father defeated Undertaker, and set the casket, which Orton locked Undertaker in, on fire.