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 attack damage
• Bonus attributes (strength/agility/intelligence)
• Bonus mana/health (static amount)
• Bonus health regeneration/mana regeneration
• Bonus attack speed
• Bonus armor
• Cleave areas
• Lifesteal
• Maim
• Movement Speed bonuses from different sources

Multiplicative stacking

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

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 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.

Evasion

The other attribute with this property is evasion.

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 crit 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 receives no benefits from Stout Shield's damage block since Kraken Shell provides better values at higher levels.

Not stacking

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.

Mechanics Stats Armor Attributes (Strength / Agility / Intelligence) Collision size Health (Health regeneration) Magic resistance Mana (Mana regeneration) Movement speed Status resistance Turn rate Vision Attack Attack animation Attack damage Attack modifier (Bash / Cleave & Splash / Critical strike / Lifesteal / Mana break) Attack range Attack speed Cast animation Cast range Damage types Motion buffer range Projectile speed Spell damage Spell lifesteal Abilities Abilities Aura Channeling Damage block Damage manipulation Damage over time Evasion Talents Teleport Status effects Attack immunity Break Cyclone Disable Disarm Ethereal Fear Forced movement Hex Hide Hypnosis Invisibility Invulnerability Leash Root Silence Sleep Slow Spell immunity Stun Taunt World Experience Gold Glyph of Fortification Map (Minimap) River Scan Runes Time of day Trees Gameplay Creep control techniques Denying Disjoint Dispel Ganking Harassment Hero complexity Initiating Item passive stacking Item sharing Jungling Lane Pushing Random distribution Roles Trap Units Ancient creeps Buildings Couriers Creep-heroes Heroes Illusions Lane creeps Neutral creeps Roshan Summons & Wards