How to get Darkrai, Shaymin, Manaphy, and Phione in Pokémon Legends: Arceus

As was the case in the original Pokémon Diamond and Pearl DS games, Manaphy, Phione, Shaymin, and Darkrai are mythical Pokémon that can only be obtained in the post-game of Legends: Arceus. That being the case, you will not be able to acquire any of these creatures unless you have beaten the main storyline and have seen the credits roll. Two of them also require that you have save files for past Pokémon games on your Switch. Then you'll need to undertake specific quests in order to unlock them. Here's what to do.

Catching Manaphy & Phione Request 66: The Sea's Legend

You do not need any additional save file information from past Pokémon games in order to see Manaphy and Phione in Pokémon Legends: Arceus.

1. You must have beaten the game's main story and seen the credits roll.
2. Return to Jubilife Village and enter the Galaxy guildhall.
3. Go into Professor Laventon's room and interact with the blackboard.
4. Accept the request titled "The Sea's Legend."
5. Now you'll need to have three Pokémon in your party: Buizel, Mantyke, and Overquil. All of them can be found in the Cobalt Coastland.
   • Buizel: Aipom Hill, Bathers' Lagoon
   • Mantyke: Ginkgo Landing, Tranquility Cove
   • Overquil: Catch Hisuian Quilfish and have it use Barb Barrage in Strong Style 20 times to evolve it.
6. Head to the arching rock formations coming out of the water in the distance.
7. Now get on Basculegion and travel to the Sea Side Hollow. It's the second cave in the cliff if you're coming from the east.Source: iMore

8. Enter the cave and you'll find one Manaphy and three Phiones.
9. I suggest manually saving before attempting to capture any of them.
10. They send out attacks that move around the room, dodge these so you don't take any damage.
11. You'll need to stun one in order to capture it. So throw Balls of Mud, Snowballs, or Spoiled Apricorns.
12. When one is stunned, let your Poké Balls fly or throw out a Pokémon to fight.

Catching Shaymin Request 92: A Token of Gratitude

In order to get Shaymin, you must have a save file for Sword or Shield on the same Switch that you're playing Legends: Arceus on. This doesn't have to be a long file at all, just enough so there is data on the console.

1. You must have beaten the game's main story and seen the credits roll.
2. Return to Jubilife Village and enter the Galaxy guildhall.
3. Go into Professor Laventon's room and interact with the blackboard.
4. Accept the request titled "A Token of Gratitude."
5. Head out to the Obsidian Fieldlands and talk to Medi to get Gracidea, an evolutionary item for Shaymin's Sky Form.
6. Head to the flower patch located at Floaro Gardens, west of the entrance to Obsidian Fields.Source: iMore

7. A cutscene will ensue and then you can catch Shaymin. Shaymin isn't skittish. So just throw some Poké Balls at it until it is captured.
8. If you want it to turn into its Sky Form, go into your Satchel and give it the Gracidea.

Catching Darkrai Request 93: The Darksome Nightmare

In order to get Darkrai, you must have save data for Brilliant Diamond or Shining Pearl on the Switch you are playing Legends: Arceus on. You don't even have to have played long, just enough so that there is data on your Switch.

1. You must have beaten the game's main story and seen the credits roll.
2. Return to Jubilife Village and enter the Galaxy guildhall.
3. Go into Professor Laventon's room and interact with the blackboard.
4. Accept the request titled "The Darksome Nightmare."
5. Make your way to the Coronet Highlands and use the tent to change to nighttime if it isn't already.
6. Head to the marker for the sidequest. It will take you southeast of Clamberclaw Cliffs.
7. If you're doing manual saves, I suggest you save now in case you accidentally defeat it without capturing it.
8. Darkrai is not easy to catch or battle. When you toss Poké Balls at it it'll immediately disappear. You need to wait until it starts screaming and then you can throw your own Pokémon at it to start the battle.
9. Whittle down its health and then throw a Poké Ball at it to capture it. It is a Dark-type, so it is weak to Fighting, Dark, and Fairy moves.

After defeating or catching Darkrai, Cael will appear and mark the task as complete.

Mythic quests

With these mythical Pokémon captured, you can work on filling out their Pokédex entries. Remember that you can only unlock the Shiny Charm, which makes it more likely to encounter shiny Pokémon, if you have gotten every Pokédex entry to level 10, so it's well worth your time to do it.