What Are Legendary Pokémon?
Throughout the years, there has been much talk of Legendary Pokémon. Starting with just the 5 Legendary Pokémon in Generation 1, as of Generation VII there are 81 different Legendary Pokémon. Legendary Pokémon are typically rare and hard to get, usually being restricted to one or two of each species in each game they're available in. Each Legendary Pokémon has an aspect of lore behind it that you can discover in the game. Before Generation IV, there were no Legendary Pokémon that could breed, before adding Manaphy and Phione. Before Generation III they couldn't have gender, and before Generation VII there were no Legendary Pokémon that could evolve. They also started to get alternate forms in Generation III and Generation IV that allowed for even more variety and lore-building.
While many people group segments of Legendary Pokémon together, there are in fact three categories of Legendary Pokémon within the game. These help determine how and when a Legendary Pokémon is used and its appearance.
Sub-Legendary Pokémon | Legendary Pokémon | Mythical Pokémon
Sub-Legendary Pokémon are the group of Legendary Pokémon that typically get no restrictions. They're allowed in Battle Facilities such as the Battle Tree, Battle Frontier, Battle Spot, Online Competitions and the Video Game Championships. They have stats that range from 534 up to 670. Their category exists within the game code for the purpose of battle regulations and display in the Alola Pokédex, but has no official name. This subcategory includes the Ultra Beasts. These are officially Legendary Pokémon in the code, but are sometimes categorised separately in other material
Legendary Pokémon are the main group of Legendary Pokémon. These Pokémon are typically the Pokémon that adorn the covers of the video games, as well as any counterparts. The first one to exist was Mewtwo but they soon became more entrenched into the lore of the games. These Pokémon are banned from Battle Tree, Battle Frontier and similar facilities, as well as the Rating Battles in Battle Spot. Several instances of the Video Game Championships and Online Competitions have allowed for the use of these Pokémon, typically with restrictions as to how many you can use. They have stats that range from 600 up to 720, and some even have Form Changes, Mega Evolutions or Primal Reversions.
Mythical Pokémon were originally known in common conversation as "Event Only Pokémon" for a reason. These Pokémon are so rare that they are typically only available through going to an event distribution and either receiving the Pokémon itself, or an item to go get the Pokémon within the wild. Due to the fact that these are typically only from events and have limited distributions, these Pokémon are banned from Battle Tree, Battle Frontier and similar facilities, as well as the Rating Battles in Battle Spot & the Video Game Championships . Several instances of Online Competitions have allowed for the use of these Pokémon. They have typically have base stats that sit around 600, and some even have Form Changes or Mega Evolutions causing stat increases.
The Generation 7 Pokémon games also introduced the first evolving Mythical Pokémon