The fourth Digimon series began airing in Japan on April 7, 2002, though it rarely aired in the UK. After prompted to do so by unusual phone messages, the five main characters go to a subway station and take a train to the Digital World, to fight the antagonist, Cherubimon and his Legendary Warrior servants before they succeed in dominating the world. Later facing a greater ordeal and threat from Lucemon and his two Royal Knights: Crusadermon and Dynasmon.