Stun

Whenever a player or monster takes damage from a hit, there is a chance they will be stunned. A stun interrupts whatever that creature was doing while a brief animation is played.

Neither damage over time nor reflect can cause stun.

Mechanics
The chance to stun is based off the damage done in a single hit compared to the target's maximum life. The default length of stuns is 350ms. A significantly long stun duration (700+ ms) will also display a swirling circle above the character or monster.

The duration of stuns can be altered by, , and similar modifiers.

Stun duration can be calculated using the following formula: $\text{ Stun duration } [ms] = 350 \times {100 + \text{Attacker's increased stun duration} \over 100 + \text{Defender's increased stun recovery} }$

Whether or not a stun occurs can be calculated using the following formula: $\text{ Stun chance } [%] = 200 \times {\text{Damage} \over \text{Defender's effective max life} }$

Where $\text{Defender's effective max life}$ in equation $$ is what the maximum life of the creature would be in a single-player map. Increases to monster life from a party of more than one player do not affect $\text{Defender's effective max life}$. For a player with Chaos Inoculation, their $\text{Defender's effective max life}$ is whatever their maximum life would be if they did not have Chaos Inoculation.

If the chance to stun would be less than or equal to 20%, it is ignored, so you need to deal more than 10% of effective maximum life to have a chance to stun. Dealing at least 50% of maximum life will always stun.

Melee damage have a +25% bonus to stun chance and non-physical damage have a -25% penalty to stun chance. Both of these will cancel each other out. Therefore, Damage can be calculated as the following: $\text{ Damage } = {(\text{Melee Physical Damage} \times 1.25) + \text{Melee Non-Physical Damage} + \text{Non-Melee Physical Damage} + (\text{Non-Melee Non-Physical Damage} \times 0.75) }$

Stun threshold
Reduced stun threshold modifiers reduce the value of $\text{Defender's effective max life}$. For example, means the enemy will be treated as if their $\text{Defender's effective max life}$ is only 75% as much as it actually is, increasing the chance that the enemy will be stunned.

When the total Stun Threshold Reduction would be over 75%, it is instead treated as being: $75 + 25 \times {(\text{Stun Threshold Reduction} - 75) \over (\text{Stun Threshold Reduction} - 50) }$

The net effect on the mean number of stuns during a monster's lifetime is as follows:
 * Hyperbolic regime: From 0 to 75% Reduced Stun Threshold, the mean number of stuns per lifetime increases from 2 to 8, accelerating as it goes.
 * Linear regime: Every 3.125% Reduced Stun Threshold past 75% increases the mean number of stuns per lifetime by 1.

If a player has a total of from gear and skills, the actual value according to equation $$ that gets used would be: $75 + 25 \times {(110 - 75) \over (110 - 50)}$ =

Stuns versus unique bosses
Unique bosses, such as Shaper, The Elder, Guardians of the Void, Elder Guardians, and Sirus, Awakener of Worlds become immune to stuns while stunned, and for 4 seconds after the fact.

Avoiding stun
There are passive skills and item modifiers that grant a chance to avoid becoming stunned:
 * As long as a creature has greater than 0 energy shield, it has a 50% chance to ignore a stun. This is calculated independently of the creature's chance to be stunned. First the chance to stun is calculated as normal, and if the stun check succeeds and would cause a stun, there is then a 50% chance that the stun can be ignored. An attack that removes energy shield can have its stun avoided, even though energy shield is 0 after damage is applied. Players lose this chance to ignore a stun with the Eldritch Battery keystone node.
 * The modifier.
 * The modifier.

The above modifiers are not doing the same thing, and apply at different times. They are not additive with each other.

A character with considerable amount of energy shield is continuously casting a spell. The character has following mods:



When the character then gets hit that normally would cause a stun. However, due to all the avoidance modifiers the actual chance to become stunned is: $(1 - 0.50) \times (1 - 0.38) \times (1 - 0.25) = %$

Unique items
Only unique items that add explicit stun-related stats are listed here.

Miscellany
These passive skills are related to stun, but do not fit in any other category:

Cluster jewel passives
The following cluster jewel-only passives are related to stun:

Version history

 * Many bosses are now immune to stun while stunned and for a short time after the stun ends.


 * Melee damage is now treated as having dealt +25% damage for the sake of calculating Stuns.
 * Elemental and Chaos damage is treated as having dealt -25% damage for the sake of stuns. This is additive with the Melee damage stun bonus, so a purely Elemental or Chaos or mixed non-physical Melee hit will see no change to previous Stun behaviour.
 * }