Complex sentence: Long presumed dead on the series, the role of the mother of leading antagonist Dr. Dorian Cramer Lord debuted onscreen played by actress Marian Seldes, who played the role from 1997 until the character's onscreen death February 13,1998.
Split into simpler sentences: Long presumed dead on the series, the role of the mother of leading antagonist Dr. Dorian Cramer Lord debuted onscreen played by actress Marian Seldes in 1997. Seldes appeared until the character's onscreen death February 13,1998.