Ogre Casters are level 38-42 monsters found in the Ogre Hole and Agara Ogres which drop level 40 armor at a 2% drop rates (according to the scan ability.)
The monsters themselves are listed as being level 46. They have 49,200 max hp and 500 mp. Their damage is 1150 and their defense is 690. (According to the scan ability.) Unlike Ogre Brutes, Ogre Casters and Ogre Arch Mages can cast spells. These spells include Fireball, Chill, and Lightning Bolt.