South of the first town, by the beach slope, there's a purple butterfly (looks like) that adds Lvl 30 Jean to your party if you interact with it.
Edit:
Is the Den of Evil supposed to be an empty, repeatable plot of random gem treasures? No enemies in there, and you can just keep going in and out to get more chests to spawn. (I guess the no enemies bit only applies to the first one actually)
Should the quests from the Ranger's guild be repeatable? Just grabbed them again after finishing them all.
Edit_2:
In the Colosseum city (second city), going in the house just east of the church actually takes you into the house connected to the Inn, just south of it.
Used 'Revert' to change back from the Earth Whelp, but the character sprite stayed as a dragon. Functionally, he changed back to human abilities.