Item passive stacking
Item passive stacking describes the interactions between multiple items that have similar effects. The stacking of items fall into different categories, and the stacking of each category is handled differently.
- Bonus attack damage
- Bonus attributes (strength/agility/intelligence)
- Bonus mana/health (static amount)
- Bonus health regeneration/mana regeneration
- Bonus attack speed
- Bonus armor
- Cleave areas
- Movement Speed bonuses from different sources
Values that are stacked in a multiplicative manner have 'diminishing returns'. This does not mean a reduction in effectiveness with multiple sources. The stacking effect can be calculated by the formula "1-(1-x)*(1-y)*(1-z)*..." where the variables x,y and z represent the individual percentages.
Magic resistance stacks in a multiplicative manner. For example when a spell deals 100 magical damage, a hero's natural 25% magic resistance reduces it to 75 damage. Now when that hero has a Hood of Defiance, the 75 damage get reduced by 25% down to 56.25 damage. If he has a 2nd hood, that 56.25 damage get reduced by 25% down to 42.1875 damage, etc. Let's take Anti-mage (25% base magic resistance) with level 4 (50% magic resistance) and a (25% magic resistance): 1-(1-0.25)*(1-0.50)*(1-0.25)=0.71875 = 71.88% magic resistance.
The other attribute with this property is evasion.
Those events stack multiplicatively, but in case two events happen at the same time, only the highest value is kept or the duration is refreshed.
The highest crit multiplier has priority in case two crits happen at the same time.
For exampleholding a (230%) cannot crit while using (350%).
Only one instance of damage block can proc at a time. The highest damage block value has priority.
receives no benefits from 's damage block since provides better values at higher levels.
The strength and damage components of multiples and s will independently stack, but the bash chance will not.
The attack speed and damage components of multiples and s will independently stack, but the chain lightning chance will not.
Auras provided by items do not stack with themselves, since they place a buff/debuff on the unit. Only the aura with the highest value will work.