I suggest you bring a Pokemon that has the move defog,and then use defog to see better while in the cave.
Chat with our AI personalities
you need azelf,uxie,mesprit to open the cave after beating the Pokemon league
USE SURF AND GO TO THE ISLAND IN THE MIDDLE, AND ENTER THROUGH THE DOOR.
Pokemon # 146 is Uxie in Pokemon diamond and Pearl and can be found in a cave at Lake Acuity just left of Snowpoint City. Pokemon # 147 Mesprit in Pokemon diamond and Pearl and can be found in a cave at Lake Verity just left of Twinleaf Town. Pokemon # 148 Azelf in Pokemon diamond and Pearl and can be found in a cave at Lake Valor between Pastoria City and Veilstone City. for a list of all other Pokemon you can check out this site... http://Pokemon.marriland.com/diamond_pearl/pokedex
Riolu, number 115 on the Sinnoh Pokedex, can be obtained as an Egg from Riley in Iron Island after helping him get through the cave.
You have to catch an Abra at a mt. cornet cave opening and train it.