transformations

[katana]

How do I get characters to transform, ie: Thief to ninja, Fighter to Knight, blah blah blah...

[Axethorn Stonehammer]

You have to retrieve the rat tail from the Castle of Ordeals for Bahamut. To reach the castle you must have either the canoe or airship and to bring it to Bahamut you must have the airship. The general concencus is that you should be level 12-14ish to do this, however it's doable earlier and should be done asap because the benefits of most classes are significant (save the BB).