Complex sentence: Jez goes to the cemetery to celebrate Mullet's death, and urinates on his grave (while claiming to himself that Mullet hanged himself to somehow get an erection), but is killed by an unseen figure, who stabs him with a cross.
Split into simpler sentences: Jez goes to the cemetery to celebrate Mullet's death and urinates on his grave (while claiming to himself that Mullet hanged himself to somehow get an erection). He is then killed by an unseen figure, who stabs him with a cross.