When you get to the arkadian ruins you will come across a room that traps you inside until you defeat the Brackish Muck creatures and the Rib Foragers/Necrophiliacs. After the battle you get 10,000 event XP. The door opens. You may then leave and turn right around again to have the whole scene replay itself. You will only get the event XP once. I am doing this on normal mode. At this point you can do the "Switch the Emeralds/Zoe Bracelet to the character about to lvl up manuever". Just enter battle and have your magic-user blast with the Mystic Cross!!! You will often get Exp Crystals and treasure chests. Around 10,000 XP upon each entry to the room. You can max all your characters out.