Complex sentence: It also introduces another Dharma station, which delves into the series' mythology, specifically the "purge" mentioned and seen respectively in the third season episodes "Enter 77" and "The Man Behind the Curtain".
Split into simpler sentences: It also introduces another Dharma station, which delves into the series' mythology, specifically the "purge". The purge was mentioned and seen respectively in the third season episodes "Enter 77" and "The Man Behind the Curtain".