Equip him/her with a Blessed Shield (bought on Norende) and the Salve-Maker's skill Healing Lore. You'll need the spells "Dispel", "Reflect", and "Raise". About battle, your amjor threat is Vistoria. Attack only her. Everytime Victor places "Fairy's Aid" on someone, remove it with Dispel. Victoria can almost insta-kill you with exterminate, so be sure to remove poison as soon as possible.