For the first time in ages, that question can legitimately be asked. By now, fans know of the 721st Pokémon, Volcanion. In the upcoming twentieth movie, Ash finds himself mysteriously bound to Volcanion as it falls from the sky and is mysteriously drawn towards a mechanical city. A corrupt minister has stolen the Artificial Pokémon Magearna and plans to use it to control the entire kingdom. Ash and Volcanion must work together to stop them in what is being called the biggest Pokémon adventure to date. Here is some info regarding Magearna since it (currently) does not exist in any Pokédex:
Magearna Type: ??? (possibly Steel and ??)
Category: Artificial Pokémon
Weight: 177.5 lbs.
Magearna is a mythical Pokémon created by man 500 years ago.