Evasion

Evasion is a passive ability that gives the unit a chance to dodge an incoming physical attack. When evaded, the attack gets completely nullified, acting as if it was disjointed. This means if the attack had an attack modifier, the modifiers are not applied either (with a very few exceptions).

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 acts if it got disjointed.

Mechanics
Evasion and Blind proc or have a chance to proc upon projectile impact. If it procs, the attack does not affect the evading unit, so that no on-attack effects are triggered. It also displays a red floating message above the attacking unit, reading "Miss", indicating that the attack missed. Furthermore, a missed attack does not play any of the attack impact sounds.

Stacking
Multiple sources of evasion stack multiplicatively, as well as other sources of miss chance such as Blind effects and the uphill miss chance. 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 evasion sources of evasion are determined by pseudo-random distribution.

Formula: 
 * Miss chance = (1 - evasion from source 1) x (1 - blind from source 2) ... x (1 - evasion/blind from source n) x uphill miss chance
 * = Πn (1 - evasion/blindn) x uphill miss chance


 * Hit chance = 1 - [(1 - accuracy from source 1) x (1 - true strike from source 2)] = 1 - Πn (1 - accuracy/true striken)


 * Final hit chance = 1 - miss chance + (hit chance * miss chance) = 1 - miss chance x (1 - hit chance)


 * Final miss chance = 1 - final hit chance = miss chance x (1 - hit chance)



I.e. 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.

Uphill miss chance
The uphill miss chance is a conditional effect, that causes 25% of the 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 attacker launches its projectile and not when it hits the target. 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 impact.

True Strike
True Stike is an attack modifier that prevents the affected 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 300 range away (the motion buffer range) before the attack. Though, projectiles of a ranged unit 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 works similar to True Strike. While True Strike prevents the unit to miss any of its attacks, Accuracy prevents the units from being missed by any attack. Just like True Strike, Accuracy works against evasion, blind, uphil miss chance and the melee motion buffer range. The unit can still disjoint ranged attack projectiles.

Sources of Accuracy