1st Generation Legendary Pokemon
Within the 1st Generation of Pokemon, there are exactly five Legendary Pokemon: Articuno, Zapdos, Moltres, Mewtwo and Mew. (Mew falls under the category of Mythical Pokemon, a given branch of Legendary Pokemon found within the Mainstream Pokemon Games.) As like all Legendary Pokemon in Pokemon GO, the 1st Generation Legendary Pokemon, at one time or another, will eventually all be released within the game as Level 5 Raid Battle Bosses (some of which already have been). Some of these Legendary Pokemon will even be restricted to EX Raid Battles.