Guard Armors are the real muscle of the enemies that appear in Experimental Staff, and they'll often back up a group of Uhran Guardsmen. Their attacks aren't as bad as you'd think (physical attacks should do 100-150 damage, and Magic Blade will do around 200 to your front row), and their high defense and HP means you'll have to invest a few turns in defeating one. They're strong against magic, so you won't be able to do much more than 200 damage with a spell. A physical attack from Seth or Kaim should do between 200 and 350 damage, or a bit more if you have a ring with Machine Killer on it, and you correctly target the enemy with the ring system.