Prospector Percy is the discoverer of the Motherlode Mine. Players can trade him golden nuggets for soft clay packs and components of the prospector outfit.
Prospector Percy can give you a challenge clue; the answer is 12. To reach him, you will need a pickaxe to mine the blocking roads leading to him.
Trivia
According to a Reddit post by Mod Reach, this character draws inspiration from Stinky Pete, the prospector in Toy Story 2. The character's overall appearance and examine text are references to this.