Head to the northwestern part of vault and go up the stairs there. Continue past the graves and over the bridge. Keep going counterclockwise until you reach a large tower where you should climb up. Ring the bell on this tower to have the Djinn jump to the ledge to the east. Now, head clockwise back around the town until you get to a bunch of graves with a dog near them. Use reveal on this area to expose a secret ladder in the middle of the graves that leads to the Vault caves. Head down this ladder, and don't fight the treasure chest that you see immediately because it's actually a Mimic. Instead, head west and then north and go through the door. The next room you'll enter has some water in it with several underwater doors and ladders. Head east and then go down the stairs to find a room with a movable torch. Move this onto the Flame square on the ground to open the gate there. Head through the door to find a room with a *lot* of water drops in it. Head north to find a door obstructed by a group of leaves. Use Ivan's Whirlwind Psynergy to open up this door. In here there's a treasure chest that has an item that will boost your attack when equipped, which is quite useful. Head back down and climb down the ladder. Freeze all of the water drops here expect for the eastern most drop, then head back up the ladder. Hop across all of the ice pillars you just made and enter the next room. In this room head down the one ladder and then up the ladder to the left of it. Head into the door, then go east a little and up the stairs. Flip the switch here to force the water into the room you were just in with the two ladders. Head back into the previous room and go down the stairs in the south part of that room. Go down the stairs again to find a room with several torches. Push the torch that has a flame on it on the flame switch to open the gate. Now, go through the gate and through the door. Take the stairs to the west and continue south through this room. You'll now be able to go down the ladder that once was drowned by water. Do so and proceed through the door into the next room. In here hop over the gap and up the ladder. Go to the next room and out the door to find yourself right under the Djinn. Go up the stairs to get the Venus Djinn Sap without a battle. Head back into the cave and use retreat to go back to the beginning. Climb up the ladder and then proceed out of Vault.