Resistance

Resistance was a combat statistic that mitigated incoming magic damage and effects. Magic spells from the following five schools could be resisted from magical resistance: Fire, Frost, Arcane, Nature, and Shadow. There was no resistance stat for Holy, and as such no players nor NPCs could resist Holy spells. A character's current resistance score to each school was advertised on the character sheet.

In PvE, resistance was highly situational and was typically only needed for certain boss encounters. The first one of this type was  Ragnaros, famous for requiring significant fire resistance on all raid members. More recently, in Wrath of the Lich King,  Sapphiron was made much easier with Frost resistance gear (although this was not necessary).

In PvP, resistance was helpful against spellcasters, although Resilience was generally considered to be a more useful stat when choosing between the two.

In Mists of Pandaria

This section concerns content exclusive to Mists of Pandaria.

Spell resistance (elemental and otherwise) is being removed as a stat and mechanic in Mists of Pandaria according to Ghostcrawler (Greg Street). Zarhym later explains that stats being sacrificed to add resistance which was only meaningful in narrow situations was a big part in removing this mechanic from the game.

Effective Resistance and Average Mitigation

The effective resistance rating of the target was calculated as follows:^{[citation needed]}

effective resistance rating = Rb + max((Lt - Lc) * 5, 0) - min(P, Rb)

Rb - target base resistance (as advertised on the character sheet)
Lt - target level
Lc - caster level
P  - caster spell penetration

In PvE boss fights, the player level was usually equal to or less than the boss level, and no spell penetration was in effect. Therefore, in this situation, it was safe to assume that the player's effective resistance was the same as the base resistance (from the character sheet).

Note that this formula rendered level 83 bosses as having 15 magical resistance against level 80 player attacks.

The percentage of magical damage that was mitigated on average was calculated by the following equation (note that this has changed in Wrath of the Lich King):^{[citation needed]}

Damage reduction percentage = 100% * effective resistance rating / ( K + effective resistance rating )

For level 80 mobs this constant K was 400. For level 83 boss mobs K was believed to be 510.

Binary Resist and Non-Binary Resist

Spell resistance was the second of two rolls to determine whether or not a spell was resisted. (Spell hit was the first roll.) The spell resistance roll would calculate in one of two different ways: one way for Binary Spells, another way for non-Binary spells. Non-binary spells were spells which only dealt damage (like [Fireball] or [Shadow Bolt]). Binary spells were spells which dealt a debuff (like [Frost Nova] or [Vampiric Embrace]) or, for some other reason, needed to take full effect or no effect at all.

For binary spells

Resistance reduced the chance for the binary spell to land by a certain percentage. Spell hit would not reduce this chance. It was assumed that this percentage was exactly the damage reduction percentage given above.^{[citation needed]}

For non-binary spells

Resistance increased the chance to suffer only a fraction of the spell's normal damage. As of Wrath of the Lich King, the possible percentages of damage resisted were weighted in sections of 0%, 10%, 20%, ..., 100% averaging to the same overall damage mitigation. However only the closest three or four sections would ever occur at a given resistance value. This allowed a sufficiently high resistance to guarantee a certain resist percentage, even in the worst case. DoT spells were considered non-binary and the partial resistance calculation was applied on each tick.

The probability of an x% resistance was given by the following formula (AR is the average resistance calculated above):^{[citation needed]}

P(x) = 50% - 250%*|x - AR|

If the probability was less than 0, it could not occur.

In Cataclysm

This section concerns content exclusive to Cataclysm.

Partial resists no longer occur against bosses.

In Burning Crusade

This section concerns content exclusive to The Burning Crusade.

In The Burning Crusade, the percent resisted had a chance to be 0%, 25%, 50%, 75%, or 100%. The probabilities were weighted such that the average damage mitigated worked out to the same percentage as with binary spells.

Sources of Resistance

Race		School	Value
	Blood Elf	All	+ 2% miss
	Draenei	Shadow	+ 2% miss
	Dwarf	Frost	+ 2% miss
	Gnome	Arcane	+ 2% miss
	Human	--	--
	Night Elf	Nature	+ 2% miss
	Orc	--	--
	Tauren	Nature	+ 2% miss
	Troll	--	--
	Forsaken	Shadow	+ 2% miss

Resistance could be obtained from buffs, potions, certain class talents, and gear. Racial abilities no longer granted magical resistance and instead granted a percentage chance to miss, as indicated by the table to the right. This chance to miss was added to the spell hit roll, and would not contribute to the non-binary damage mitigation.

Stacking

The following list contains sources of resistance and stacking information. Each line will stack with other lines.

• Self-only buffs, such as Mage Armor stack freely;
• Equipped items and enchants stack freely;
• Auras, Shaman totems, raid buffs (e.g. Gift of the Wild, Prayer of Shadow Protection), and [Magic Resistance Potion] do not stack with themselves - only the highest single effect of these will apply;
• Elixirs and Flasks providing resistance do not stack with themselves.

Example

In a group where Mark of the Wild, Aspect of the Wild, and Nature Resistance Totem is active, the group will only receive 130 Nature Resistance (either from the aspect or totem).

Effectiveness of Resistance

The damage absorbed per point of damage/healing/tanking stat lost decreased as resistance was gained, similar to armor. However guaranteeing a certain resistance percentage could be valuable, especially in fights with a large spike of elemental damage.

See also

• Formulas:Magical resistance
• [Resistance Aura]
• Resistance equipment
• Racial traits
• Spell penetration

External links

WoW Insider Blogs related to Resistance

       WoW Insider Blogs related to Arcane Resistance

       WoW Insider Blogs related to Fire Resistance

       WoW Insider Blogs related to Frost Resistance

       WoW Insider Blogs related to Nature Resistance

       WoW Insider Blogs related to Shadow Resistance