Do not just throw your highest-level characters together. Grouping 2 or more heroes of the exact same element gives your team a massive health and attack bonus.
He is your main character. If Rudy dies, the game ends immediately because your computer-controlled allies cannot use elixirs to revive you. brave-soul
She is your primary white mage. It is highly recommended to recruit her into your party and unlock her ending first so she can learn the vital "Resurrection" spell. Do not just throw your highest-level characters together