Unlike QFG2, where any character class could become a paladin, in QFG3: Wages of War, only the Fighter has this opportunity. Both the Thief and the Wizard are disqualified due to certain actions they are required to do in this game.

The Do's and Don't's of becoming a Paladin for your Fighter are:

If you fulfill these criteria, you are sent back to Tarna to Kreesha's house following the Spear Ceremony, before the Peace Conference. There Rakeesh will proclaim you a Paladin and give you his sword Soulforge.