Paira has been seeing something strange out in the wilderness. She believes she is seeing a will-o-wisp up in the trees between Windswept Run and Nature’s Pantry. It’s time to investigate this strange appearance. Here is how you complete the Mysterious Will-O’-the-Wisp request in Pokémon Legends: Arceus.
You will find Paira across from the pasture in Jubilife Village. You won’t be able to accept this request until later in the game when you have calmed Kleavor. Talk to Paira and she will tell you about her will-o-wisp sighting. Head out of town and select the Heights Camp as your destination to make things a little easier.
From the Heights Camp, head south down the mountain to where the marker appears on your map. You will end up finding a large tree. Interact with the tree to get a cutscene where you see a Chimchar hanging onto the top of the tree. The Chimchar will jump down and attack. Battle the Chimchar, but don’t defeat it. Paira wants you to capture it (plus, this might be your first Chimchar encounter).
After you capture the Chimchar, head back to Jubilife Village and talk to Paira. After realizing it was a pokémon behind her strange sighting, she will reward you with two small experience candies.