Evasion

Evasion is a passive ability that gives the weilding unit a chance to evade an incoming physical attack.

Additional Information
Only physical attacks but no spells can be evaded by passive Evasion. However, abilities like Blink or Shadow Walk can be used to dodge attacks or projectile-based abilities such as Vengeful Spirit's Magic Missile. The item Monkey King Bar is a direct counter to Evasion, as its True Strike ability causes the weilder's attacks to never miss.

Stacking
Evasion never stacks. This includes both Hero Abilities and Item bonuses, only the one with the highest probability will work. An exception to that rule is Faceless Void's Backtrack ability, as it is not considered Evasion. Evasion and Backtrack work independantly and are subject to Chance Stacking. The Blind status effect also stacks diminishly with Evasion.

Sources of Evasion