How do I beat Corvus in Dragon Quest IX?

You may want to consider switching someone to paladin and getting the class skills, as the added defense will be extremely helpful, as well as forbearance. There's no trick to beating Corvus, just tension for extra damage and ueber falcon blade's falcon slash on high damage characters. Keep your party healed and buffed as best as you can. If you still can't manage, level up other jobs and put the skill points in good support trees, such as paladin, martial artist, thief, and armamentalist. Once you've put the points into armamentalist, you can also use Corvus's corresponding fource weakness (sorry, I don't know it), which will cause extra damage. Good luck!