For Von Leon, do the following :D
Prequests:
Step 1 - Go to Murt in Lion King's Castle : Second Tower and accept the quest for Murt's Letter
Step 2 - Head back to El Nath & talk to Alcaster in the El Nath Market and do the follow up quest
Step 3 - Head back to Murt and use the Crystal you received from Alcaster in that map
Step 4 - Accept Ifia's quest
Step 5 - Go to Luden in Lion King's Castle : Fourth Tower and accept the quest The Transformed King
Step 6 - You must kill 33 Grey Vulture's.
This part you must do every time you want to enter!
Step 7 - Talk to Luden to accept the quest The Knight's Magic Scroll
Step 8 - You must kill Castle Golem's until a Dirty Scroll drops.