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.^[1]

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.^[2] A significantly long stun duration (700+ ms) will also display a swirling circle above the character or monster.^[3]

The duration of stuns can be altered by increased Block and Stun Recovery, increased Stun Duration on enemies, increased Stun Duration with Two Handed Melee Weapons on enemies and similar modifiers.

Stun duration can be calculated using the following formula:^[2]

$\color[RGB]{163,141,109} \text{ Stun duration } [ms] = 350 \times {100 + \text{Attacker's increased stun duration} \over 100 + \text{Defender's increased stun recovery} }$

(1)

Whether or not a stun occurs can be calculated using the following formula:^[2]

$\color[RGB]{163,141,109} \text{ Stun chance } [\%] = 200 \times {\text{Damage} \over \text{Defender's effective max life} }$

(2)

Where $\color[RGB]{163,141,109} \text{Defender's effective max life}$ in equation (2) 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 $\color[RGB]{163,141,109} \text{Defender's effective max life}$ . For a player with Chaos Inoculation, their $\color[RGB]{163,141,109} \text{Defender's effective max life}$ is whatever their maximum life would be if they did not have Chaos Inoculation.^[2]

If the chance to stun would be less than or equal to 20%, it is ignored,^[4] 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:

$\color[RGB]{163,141,109} \text{ Damage } = {(\text{Melee Physical Damage} \times 1.25) + \text{Melee Non-Physical Damage} + \text{Non-Melee Physical Damage} + (\text{Non-Melee Non-Physical Damage} \times 0.75) }$

(2)

Stun threshold[]

Reduced stun threshold modifiers reduce the value of $\color[RGB]{163,141,109} \text{Defender's effective max life}$ . For example, 25% reduced Enemy Stun Threshold means the enemy will be treated as if their $\color[RGB]{163,141,109} \text{Defender's effective max life}$ is only 75% as much as it actually is, increasing the chance that the enemy will be stunned.^[2]

When the total Stun Threshold Reduction would be over 75%, it is instead treated as being:

$\color[RGB]{163,141,109} 75 + 25 \times {(\text{Stun Threshold Reduction} - 75) \over (\text{Stun Threshold Reduction} - 50) }$

(3)

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.

Example ▾ [Expand] ▾

If a player has a total of 110% reduced Enemy Stun Threshold from gear and skills, the actual value according to equation (3) that gets used would be:

$\color[RGB]{163,141,109} 75 + 25 \times {(110 - 75) \over (110 - 50)}$ = 89.6 reduced Enemy Stun Threshold

Reduced threshold	Eff. reduced threshold	Min life for stun	Min life for 100% stun
0%	0%	10%	50%
5%	5%	9.5%	47.5%
10%	10%	9%	45%
15%	15%	8.5%	42.5%
20%	20%	8%	40%
25%	25%	7.5%	37.5%
30%	30%	7%	35%
35%	35%	6.5%	32.5%
40%	40%	6%	30%
45%	45%	5.5%	27.5%
50%	50%	5%	25%
55%	55%	4.5%	22.5%
60%	60%	4%	20%
65%	65%	3.5%	17.5%
70%	70%	3%	15%
75%	75%	2.5%	12.5%
80%	79.2%	2.08%	10.4%
85%	82.1%	1.79%	9%
90%	84.4%	1.56%	7.8%
95%	86.1%	1.39%	7%
100%	87.5%	1.25%	6.25%
105%	88.6%	1.14%	5.7%
110%	89.6%	1.04%	5.2%
115%	90.4%	0.96%	4.8%
120%	91.1%	0.89%	4.5%
125%	91.7%	0.83%	4.2%
130%	92.2%	0.78%	3.9%
135%	92.6%	0.74%	3.7%
140%	93.1%	0.69%	3.5%
145%	93.4%	0.66%	3.3%
150%	93.8%	0.62%	3.1%

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.^[5] 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.^[6]
The modifier +#% chance to Avoid being Stunned.
The modifier +#% chance to Avoid interruption from Stuns while Casting.

The above modifiers are not doing the same thing, and apply at different times. They are not additive with each other.^[7]^[8]

Example ▾ [Expand] ▾

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

+38% chance to Avoid being Stunned
+25% chance to Avoid interruption from Stuns while Casting

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:

$\color[RGB]{163,141,109} (1 - 0.50) \times (1 - 0.38) \times (1 - 0.25) = 23.25\%$