Complex sentence: A total of seven different story arcs were originally planned for Bionicle's outlined twenty-year tenure, but only three were ever completed, while the fourth was altered to end the story as a whole due to Lego's decision to discontinue the theme.
Split into simpler sentences: A total of seven different story arcs were originally planned to be carried out over Bionicle's outlined twenty-year tenure. Only three were ever completed, while the fourth was altered to end the whole story due to Lego's decision to discontinue the theme.