Complex sentence: Legacy is a prequel to the original game, explaining the background stories of several characters from the series, demonstrating their reasons for participating in the upcoming tenth Mortal Kombat tournament, on which the first game was based.
Split into simpler sentences: Legacy is the prequel to the original game, explaining the background stories of several characters from the series. It culminates by demonstrating the characters' reasons for participating in the upcoming tenth Mortal Kombat tournament, on which the first game was based.