Legendary Pokémon are Pokémon that are very rare, and there is usually only one in each game. Examples of legendaries are Articuno, Zapdos, Mewtwo, Lugia, Groudon, and Dialga. They are hard to catch, and are stronger than most Pokémon. Some roam around, while others can be found in one spot until you KO or capture them. If you KO a legendary, it will usually leave and will never be found again unless the game is restarted or the Elite Four is defeated again. Because of this, players usually save before engaging the Pokémon.