Stunned enemies and players cannot move or use skills. Stun has a base duration of 0.4 seconds.
All hits have a chance to stun if they deal enough damage. Hits that deal more damage are more likely to stun, but enemies that have higher maximum health are harder to stun.
The Increased Stun Chance stat also makes hits more likely to stun, while the target’s Stun Avoidance stat makes it harder to stun. If the target is shocked, it has an increased chance to be stunned.
The stun chance of any hit can be calculated using this formula:
When calculating stun chance using the formula above, melee damage dealt by players is multiplied by 3, and other damage dealt by players is multiplied by 2.
Bosses are harder to stun. In the calculation above, their maximum health is 50% higher. So if a boss has 10 000 health, for the stun calculation 15 000 is used instead.
Due to the formula above, at 0% increased stun chance and 0 stun avoidance, non-player hits must deal more damage than 5% of a target's maximum health to have a chance to stun them. Every 100 stun avoidance raises this threshold by 1%. This threshold is reduced by increased stun chance, and by the player bonuses described above.
Players have inherent stun avoidance equal to 250 + 5 per character level, and can acquire more through items, passives and blessings.