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.

Independent stacking

• Bonus 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

Multiplicative stacking

Values that are stacked multiplicatively have diminishing returns. 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

Magic resistance stacks multiplicatively. 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 30% down to 52.5 damage. If he has a 2nd hood, that 52.5 damage get reduced by 30% down to 36.75 damage, etc. Let's take Anti-mage (25% base magic resistance) with level 4 Spell Shield (50% magic resistance) and a Hood of Defiance (25% magic resistance): 1-(1-0.25)*(1-0.50)*(1-0.25)=0.71875 = 71.88% magic resistance.

Limited stacking

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.

Critical Strike

The highest multiplier has priority in case two crits happen at the same time.

For example Tusk holding a Daedalus (230%) cannot crit while using Walrus PUNCH! (350% ).

Damage Block

Only one instance of Damage Block can proc at a time. The highest damage block value has priority.

Tidehunter has no use for a Stout Shield (16), once he skilled Kraken Shell (12/24/36/48) past level 2.

Maim

[ Info Needed ]

Not stacking

Bloodstone

Multiple Bloodstones do not reduce respawn time further. Only the Bloodstone in the highest priority slot works.

Priority slots are as follows:

1 2 3

4 5 6

Bash

The strength and damage components of multiple Skull Bashers and Abyssal Blades will independently stack, but the bash chance will not.

Chain Lightning

The attack speed and damage components of multiple Maelstroms and Mjollnirs will independently stack, but the chain lightning chance will not.

Auras

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. Note that some items share a specific aura ( Ring of Basilius and Vladmir's Offering). In this case, only Vladmir's Offering's mana regeneration aura and armor aura will work.

Unique Attack Modifiers

An attack can only have one Unique Attack Modifier. Priorities are explained here.