The Charm Lost in the Swamp is a side request in Pokemon Legends: Arceus that tasks you with finding a charm that Yojiro lost while he was being chased by an alpha Hippowdon. The clue to this quest is that there is only one alpha Hippowdon on this map, once you know where this is, you will be able to locate the charm.
Where to find the Charm in the Swamp
If you head down the hill from where you first speak with Yojiro, you will find a large area of mud with lots of hippo Pokemon. These can be aggressive so make sure you have some good Pokemon in your party. In the middle, you will see the alpha, check the map below to see the exact location.
Finding The Charm After Defeating the Hippowdon
Once you have defeated the Hippowdon, you will notice that you did not automatically receive the charm. This is because you still have to find the location. If you search around the pool of mud where you found the alpha, you will see a star-shaped sparkle just above the water’s surface. Go over and interact with this and you will receive the charm.