Complex sentence: Meleagros led a hunting party to slay the Calydonian Boar, which was set loose upon Calydon by Artemis, who was displeased at the Calydonian king for neglecting to make a proper sacrifice to her.
Split into simpler sentences: Meleagros led a hunting party to slay the Calydonian Boar, which was set loose upon Calydon by Artemis. He was displeased at the Calydonian king for neglecting to make a proper sacrifice to her.