In order for the quest to be available to you, you must use Aisha and must be level 15 and above. Otherwise, the quest won't appear in your Quest Log. Enter the Underground Waterway under the Very Hard mode to collect 10 Dead Tree Branches and 30 Runic Power Crystal from the Ghost Magician and White Ghost Magician, respectively. The task is fairly easy, especially if you're in a party for quick raid. Buy these from the Potion NPC in Elder Village. The Suburbs of Wally's Castle can be found in Elder Village map. Enter the dungeon under Very Hard mode and do the following:  Kill 14 Jangos and 14 Kid Phorus Clear the dungeon with B rank. Collect 3 Quest Items from Bomber Mongs and 1 Special Nut from William After you have completed the quest, return to the village and check your Quest Log. Hand in your quest items by clicking Complete Quest, or talk to the bulletin board found in the low middle level of the village. You can now proceed to choosing the quest for one of the three advance classes for Aisha.

Summary:
Get qualified. Infiltrate the Underground Waterway. Gather 5 Medium MP Potions. Enter the Suburbs of Wally's Castle. Return to Elder Village.