Evasion

Evasion is mechanic that allows the unit to dodge an incoming attacks. When evaded, the attack gets completely nullified. This means, anything that relies on attacks to hit their targets do not trigger, which includes most attack modifiers, and on-hit effects.

A similar mechanic to evasion is blind. While evasion makes a unit evade incoming attacks from other units, blind makes a unit miss upon attacking other units. Just like evasion, when an attack misses to blindness, it gets completely nullified.

Mechanics
Evasion and blind trigger upon landing an attack, which is on projectile impact for ranged units. If it triggers, the attack does not affect the evading unit at all, so that no on-attack effects are triggered. Upon missing an attack on an enemy, a red floating text appears, reading "miss", visible to the attacking player only. The enemy, who was just missed by an attack, also sees a floating text, but in white and reading "evade" instead. Furthermore, a missed attack does not play any of the attack impact sounds.

Stacking
Multiple sources of evasion stack multiplicatively with each other, while sources of blind effects stack additively with each other and multiplicatively with evasion. The uphill miss chance stacks multiplicatively with evasion and blind. While the actual chance to evade is diminishing, each source of evasion increases effective HP against physical attacks more than the last due to evasion's exponential nature. The chances of all sources of evasion are determined by pseudo-random distribution, while the chances of blind are determined by true random distribution.

Formula:

E.g. for Butterfly the chance to get hit is 65% because Butterfly has 35% evasion. The source of evasion values must be expressed in hundredths (so if we have 50% evasion, the value needs to be 50/100 = 0.50).

As an example, if Phantom Assassin has Level 4 Blur (0.5 chance to get hit) and Butterfly (0.65 chance to get hit), her chance to get hit by attacks is 0.5 * 0.65 = 0.325 or 32.5%. A more concrete way of thinking about evasion stacking is that for an attack to bypass an evasion stack and connect, it should bypass each source of evasion in sequence. Only if all sources of evasion fail, is the attack able to deal damage.

Evasion granting talents
The following heroes have a talent that grants them evasion.

Uphill miss chance
The uphill miss chance is a conditional effect, that causes 25% of the ranged attacks to miss if the attacker is at a lower terrain level as the target. It does not matter how many terrain levels difference is between them, the miss chance stays 25%. The terrain level difference of the attacker and the target is taken into account when the projectile hits the target and not when the attacker launches it. Thus, an attack can still miss due to the uphill miss chance even when both the attacker and the target stand at the same elevation level upon projectile launch. Melee units and flying units are unaffected by this and cannot miss due to elevation differences.

True Strike
True Strike prevents the unit's attacks from missing, negating evasion, blindness and the 25% uphill miss chance for ranged units. It also prevents melee attacks from missing when the target moves more than 350 range away before the attack. Although unable to miss, attack projectiles of a ranged units with True Strike can still be disjointed. True Strike does not work when attacking buildings. However, it works against any other unit, including wards and allied units.

Sources of True Strike

Accuracy
Accuracy may refer to two different things:
 * It may refer to true strike's counterpart. While True Strike prevents the unit to miss any of its attacks, accuracy prevents the units from being missed by any attack.
 * It also may either refer to chance-based true strike, where attacks gain a chance to ignore evasion and blind effects.

Sources of Accuracy by first definition

Sources of Accuracy by second definition