Evasion

Evasion is the first layer of defence that increases a character's chance to evade incoming attacks. Evasion is opposed by the attacker's accuracy. Along with armour and energy shield, evasion is one of the three defence types that can implicitly appear on equipment.

All classes start with base evasion rating and gain  additional evasion per level. The first level is included in this, so a level 1 character will have base evasion. This gives a base of evasion at level 100.

Dexterity also grants bonuses to evasion. Every 5 points of dexterity provide. Non-multiples of 5 will be rounded up to the nearest multiple of 5 (e.g. 142 dexterity will be rounded to 145).

Mechanics
Evading an attack prevents all damage and other harmful effects including status ailments and stun. Only melee and ranged attacks can be evaded; spells automatically hit. The chance to evade an attack is based on the defender's evasion rating compared to the attacker's accuracy.

$\text{Chance to Evade} = 1 - {\text{Attacker's Accuracy}*1.15 \over \text{Attacker's Accuracy} + (\text{Defender's Evasion} \times \frac{1}{4}) ^ {0.8} }$

The Chance to Evade is limited to between 0% and 95% (directly affected by the limits of Chance to Hit).

There are two modifiers which bypass evasion:  (from for example the Unwavering Stance keystone or ), and attacks using Hits can't be evaded.

Evasion also gives an implicit chance to not receive critical strikes from attacks. If an incoming critical strike hit succeeds the initial hit/miss roll, a secondary check is performed to determine critical hit or normal hit. If the first rolls succeeds but the second roll fails, only a normal damage hit is applied. Since spells cannot be evaded, spell criticals also cannot be evaded.

Evasion does not calculate the chance of each hit independently. Instead, it uses a system of "entropy" to ensure that enemies won't get long strings of hits or misses by chance. To summarize, these are the calculation steps in each attack:
 * 1) If it is the first time an entity is attacked, or if the time between the last attack and this one is larger than 100 server ticks (3.33 seconds), randomise the entropy from 0–99.Evasion-percent.png
 * 2) Calculate chance to hit of the attacker using the above formula, and add this integer to the entropy counter.
 * 3) If this is 100 or greater, the check counts as a hit. Subtract 100 from the entropy counter. Otherwise it is a miss and the entropy counter doesn't change.
 * 4) A critical hit is evaded on a separate random roll and will not affect this entropy value.

As a result, if a player has a 1 in N chance to be hit, then the player will be hit exactly once for every N consecutive attacks. This eliminates all possibilities of lucky and/or unlucky streaks. It is still based on chance because of the entropy counter's randomization in the first step. Note that if multiple mobs are attacking one character, all of the mobs' attacks share the same entropy counter. Also note that the chance to evade calculation on the character page is based on the average accuracy of a monster at the player's level.

Interaction with Dodge
Chance to Dodge bonuses granted by sources like Acrobatics function similar to evasion, but are rolled separately and are true random rather than entropy-based. Phase Acrobatics grants a chance to dodge spells.

Assuming a character has a 40% chance to evade and a 20% chance to dodge, a character has a 52% chance to prevent receiving a hit.

$\text{Chance}_{\text{Prevent Attack} } = 1 - (1 -\text{Chance}_{\text{Evade} }) \times ( 1 - \text{Chance}_{\text{Dodge} })$

Modifiers to chance to Hit and chance to Evade
Certain modifiers can be directly applied to the and  stats, such as blind, Arrow Dancing, and Garukhan's Pantheon power. The order in which these take effect are as follows; chance to hit is determined based on the attacker's accuracy and the defender's evasion, then modifiers to the attacker's chance to hit get applied, after which modifiers to the defender's chance to evade are applied to get the final chance to evade/hit.

Example 1
A player is fighting three monsters, one (A) with a 70% chance to hit and two (B, C) with a 45% chance to hit.
 * A attacks. The player's entropy is a random number between 0-99, in this case 37.
 * A adds 70 to the counter, raising it to 100 or greater, and hits. 100 is subtracted and the counter is now 7.
 * B attacks, adding 45. 52
 * C attacks, adding 45. 97
 * A attacks, adding 70. This hits and the counter becomes 67. It happens to be a critical strike, which means it has a 70% chance to do bonus damage. This roll is independent and doesn't affect entropy.
 * The player runs away for >6 seconds, so a new entropy value will be rolled on the next attack.

Example 2
A player has 5000 evasion, and gets 20% more Chance to Evade from Ghost Dance, and is attacked by a monster with 500 accuracy who is blinded.


 * Chance to Hit = 500 / ( 500 + (5000/4)^0.8 ) = 62% Chance to Hit.
 * Blind lowers the chance to hit by 50% to 31%, meaning the player has a 69% chance to evade.
 * Shade Form's 20% more Chance to Evade causes the final chance to Evade to be 69% * 1.2 = 82%.

Mechanics Scaled by Evasion Rating
The following items provide some bonuses that scale with evasion rating.

Notable Evasion Rating
Unique items that can potentially grant upwards of 1,000 Evasion rating.

Global Evasion increases
Unique items that grant increased global Evasion rating.

Global flat Evasion
Unique items that grant a flat bonus to global Evasion rating.

Passive skills
There are passive skills that grant evasion bonuses.

Evasion rating
These passive skills grant increased evasion rating or additional base evasion rating.

Miscellany
These passive skills are related to evasion, but do not fit into any other category.

Version history

 * Accuracy is no longer capped to a 95% chance to hit. With enough accuracy, an enemy will never be able to evade an attack, so you will no longer have lone surviving monster frustratingly taunting you (unless you didn't get enough accuracy!).
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