Magic Damage Reduced applies to any magic and elemental (fire, lightning and cold) damage remaining after Cyclone Armor and then Energy Shield have been applied. MDR applies to each separately, so an attack applying 20 magic, 20 fire, 20 lightning and 20 cold damage would apply no damage after MDR 20 was applied. 
- Effectiveness is reduced when applied to magic or elemental damage applied by the following missile attacks:
- When MDR completely negates magic and elemental damage, it does not matter if Lower Resist, Conviction or -% Enemy Resistance then reduce resistance, since there is no damage to which resistance can be applied (although resistance will still apply to cold length or freeze length).
- A combination of resistance and Absorb is generally more effective at significantly reducing or even negating magic and elemental damage.
- When an attack applies magic or elemental damage and physical damage, and MDR > magic or elemental damage, the excess is applied to physical damage after Damage Resist or Damage Reduced by % has been applied.  
- For example, an attack applying 100 physical damage and 50 fire, 50 lightning and 50 cold damage to a target with MDR 100 and DR 50%, would apply no fire (50-100 = -50), lightning (-50) or cold (-50) damage and 50 physical damage before excess MDR (-150 in total) applied: this would result in no (50-150 < 0) damage.