MDEF

The Magic Defense STATISTICS shows how well a character can take magic damage. The Magic Defense STATISTICS is a percentage that is based on both Races and Classes. the base amount range from 1%-15%. This percentage represents how much damage is taken off of Magic attacks.
For information on how to increase, see DEX
EX) you were hit with 200 magic damage and your magic defense is 10%. that means 20 damage is taken off so you are only hit with 180 magic damage.

MDEF

Ragnaros: Exodyn Saga xBatteries