There are very few Pokemon in Kanto whose rarity is so extreme that legends are created from them. While on your adventure, you might hear these tales, or someone important will tell you rumors of ultra powerful Pokemon hiding away in certain dungeons.
In Pokemon Let’s Go Pikachu and Let’s Go Eevee, finding stationary Pokemon are a bit different from encounters with all other wild Pokemon. After finding a legendary Pokemon standing in its dungeon, you must defeat it in battle within five minutes before you’re given the chance to throw a Poke Ball. If you can’t defeat it in five minutes it will run away from battle.
After becoming Pokemon League Champion, the three legendary birds will begin to appear in the skies of Routes 1-25. In order to reach them, you must fly on the back of a large Pokemon. Charizard and Dragonite will also begin to appear in the skies.
Articuno is one of the three legendary birds in Pokemon Let’s Go. This Pokemon can be found waiting at the bottom of the Seafoam Islands. Before you can reach it, you’ll need to push a few boulders down several holes to block off the rapid river to Articuno. Teach your Partner Pokemon the secret technique Strong Push to send these boulders down to the dungeon’s basement.
Zapdos is one of the three legendary birds in Pokemon Let’s Go. This Pokemon can be found waiting near the exit of the Power Plant, which is located downstream on the east side of Route 10. Teach your Partner Pokemon the secret technique Sea Skim to reach it.
Moltres is one of the three legendary birds in Pokemon Let’s Go. This Pokemon can be found waiting in the basement of Victory Road.
Mewtwo is the strongest Pokemon in Kanto. He can be found waiting at the bottom of the Cerulean Cave, which is northwest of Cerulean City. A man will be blocking the entrance to the dungeon until you become the Pokemon League Champion.