Legend of the Mysterious Ruins (Japanese: なぞの いせきの でんせつLegend of the Mysterious Ruins) is a series of Challenge Requests in Pokémon Mystery Dungeon: Gates to Infinity that allows the player to battle special Legendary Pokémon. These job requests will randomly appear on the Challenge Board after defeating Bittercold. By accepting the request, the player can access special areas where the Legendary Pokémon reside. The Legendary Pokémon in these requests are unrecruitable.
As with other Challenge Board requests, the player will be rewarded with rarer items such as Heal Seeds, Revivier Seeds, Gold Ribbons, Pass Scarves, Insomniscopes, and Heart Pendants. Each dungeon has the boss with seven levels of difficulty. The mission difficulty can be determined from the rating in stars (ranging from 6-9), and more difficult missions will reward the player with rarer items and more Poké*.