Complex sentence: The show opened with Sabu versus Abyss in the (first-ever) "Barbed Wire Massacre", in which the ring ropes are replaced with barbed wire, and the only way to win is by pinfall or submission.
Split into simpler sentences: The show opened with Sabu versus Abyss in the first-ever Barbed Wire Massacre. In this match, the ring ropes were replaced with barbed wire, with the only way to win being pinfall or submission.