Orb Effects Stacking

There are certain skills that add bonuses or effects to the damage that they deal on an attack, some of those place certain indicators or "buffs" on the target (sometimes to deal damage per second or other timed effects), note that buffs are not always visible under the status bar

Blizzard imposed certain restrictions regarding the behaviour of these "Buff Placers"
probably for balance reasons

There are also other skills (which fall under the "Orb Effect" naming), which are based on abilities that were originally used on the "Orb" items in ladder Warcraft III. A restriction was also imposed on those skills because said effects were considered too powerful to be stacked (meaning bought in quantities to increase the effects), an "Orb Effect" skill may or may not be a buff placer.

Hence the two famous rules:

• Orb Effects do not stack (you will only get the effect of one "orb" skill)
• You can only place one buff per attack

Some effects aren't considered Orb Effects or Buff Placers, but are attack modifiers nevertheless, of which one good example is Cleave.

Melee Units

Skills/Items	Stacking
					(Melee)		Critical Strike	Bash
	Place	Place	Corruption	Lifeleech	Place	Corruption	Both	Both
	Place	Place	Chance Effect	Lifeleech	Place	Overrides on proc	Both	Both
	[1] Else Slot Priority	Latest	Chance Effect	Lifeleech	[1] Else Slot Priority	Overrides on proc	Both	Both
	Corruption	Chance Effect	Latest	Lifeleech	Skadi	[4]	Both	Both
	Lifeleech	Lifeleech	Lifeleech	Place	Lifeleech	Both	Both	Both
	Place	Place	Skadi	Lifeleech	Place	Skadi	Both	Both
	Incinerate	Incinerate	Incinerate	Incinerate	Incinerate	Incinerate	[1] Else Both	[1] Else Both
	Corruption	Overrides on proc	[4]	Both	Skadi	Latest	Both	Both

Ranged Units

Skills/Items		Type		Stacking
		Orb	Buff Placer					(Ranged)		Critical Strike	Bash
		Always	Always	Place	Place	Corruption	Lifesteal	Corruption	Corruption	Critical Strike	Bash
		Always	On Proc	Place	Place	Chance Effect	Lifesteal	Chance Effect overrides on proc	Chance Effect overrides on proc	Critical Strike	Bash
				[1] Else Slot Priority	[1] Else Slot Priority	Only on the Bonus Shot	Lifesteal	Check Note [2]	Check Note [2]	Critical Strike	Bash
		Always	Always	Corruption	Chance Effect	Latest	Lifesteal	[3]	[3] if feedback was acquired later, else only OoV	Critical Strike	Bash
		Always	Never	Lifesteal	Lifesteal	Lifesteal	Place	Both	Both	Both	Both
(Ranged)		Never	Always	Corruption	Chance skill overrides on proc	[3]	Both	Frost Attack	Poison Attack	Critical Strike	Bash
(Melee)		Always	Always	Place	Place	Frost Attack	Lifesteal	Frost Attack (Melee Skadi)	Frost Attack	Critical Strike	Bash
	Single Cast	Toggled	Never	Searing Arrows	Searing Arrows	[1] else [3]	Lifesteal	Both	Both	Searing Arrows	Searing Arrows
	Auto Cast			Searing Arrows	Searing Arrows	Searing Arrows	Searing Arrows	Both	Both	[1] Else Item	[1] Else Both
	Single Cast	Toggled or Cast	Toggled or Cast	Arrow Effect	Arrow Effect	[1] else [3]	Lifesteal	Arrow Effect	Arrow Effect	Manual Cast: Will not Bash or Crit. Auto Cast: If you got the item before leveling the skill then you will not Bash or Crit. If you acquire the item after leveling the skill it will override on Proc, but it will still consume Mana and show the projectile.
	Auto Cast			Arrow Effect	Arrow Effect	Arrow Effect	Arrow Effect	Arrow Effect	Arrow Effect
		Never	Always	Corruption	Chance Effect overrides on proc	[1] else [3]	Both	Poison Attack	Latest	Critical Strike	Bash

Other Attack Modifiers

Skills/Items	Stacking
				(On Main)	(Ranged)	(Melee)		Critical Strike (On Main)	Bash (On Main)
Moon Glaives	No Attack	No Attack	Moon Glaives	Both	Moon Glaives	N/A	Moon Glaives	Critical Strike	Bash
Split Shot/Flak Cannon	Corruption	Chain Lightning on main target	[1] else[3]	Both	Both but Frost Attack only on main target	N/A	If the item was acquired during the skill's duration: only Poison Attack. Else: skill + Poison Attack on main target	Critical Strike	Bash
Splash from Elder Dragon Form Lvl 2	Splash	Chance Effect on main target, Splash	Splash	Both	Splashed Frost Attack	Frost Attack + Splash	Splash	Critical Strike + Splash	Bash + Splash
Frost Attack and Splash attack from EDF Lvl3	Splash	Chance skill overrides Frost on proc, Splash works all the time, if the attack has Frost it will be splashed	Splash + Frost	All	If item first: skill will be splashed, else item Splashed	Frost Attack + Splash	Frost Attack and Splash attack from EDF Lvl3	Critical Strike + Splash	Bash + Splash

Notes

[1]	If the item was acquired (bought, picked up, received) before the first level of the ability only the ability will work
[2]	If Weaver auto-acquires his target it will slow while Geminate Attack is on cooldown, if he is ordered to attack it will slow on every hit except the one before the extra attack.
[3]	Only Feedback will work if the target unit has Maximum Mana > 0
[4]	Both if feedback was aquired later, else last aquired.
"Place"	Means: You will get the effect of the item in the highest priority slot. Order is (from highest to lowest): Top Left (1), Top Right (2), Mid Left (3), Mid Right (4), Bottom Left (5), Bottom Right (6)
"Slot Priority"	Item overrides if it's in the Top Left Priority slot, else skill works
Arrow Skills when Crit procs	Mana will still be lost if the Critical Strike overrides the arrow effect

Critical Strikes and Bashes

A Critical Strike is a ladder-based ability that gives the chance to deal a bonus percentage damage on a succesful attack of the weilding unit.

• Critical strikes are buff placers on the attack that trigger them, only for ranged units.
• Critical Strikes deal the same Attack type as the attacker but with Damage Type Normal (Physical, reduced by armor amount and type)

Stacking:
When two Critical Strikes proc at the same time only the last acquired will work, a skill is considered acquired when the first level is learned, and an item is considered acquired when it's picked up.
The red number shown by Critical Strike is displayed before reductions (this is why images don't show very low red numbers)

A Bash is also a ladder-based skill that gives a chance to deal a fixed amount of bonus damage and stun the target for any duration.

• Bashes are buff placers on the attack that trigger them, only for ranged units.
• Bonus damage from Bash on a ranged unit will be added to the unit's damage and not dealt separately, this is why you can Lifesteal off MKB.
• For ranged units Bashes deal Physical bonus damage (Reduced by armor type and amount) and magical stun (Blockable by Spell Immunity)
• For melee units Bashes deal Magical bonus damage (Reduced by spell resistance and blocked by spell immunity) and physical stun (not blockable by spell immunity), the damage is dealt separately.
• The stun duration of any bash will not override another stun duration that is longer (if try you stun someone that has 0.5 seconds of stun remaining with a 0.01 seconds stun yours will be ignored but the damage dealt)

Stacking:
When two bashes proc at the same time on a ranged hero only the last one acquired will work (stun and damage wise)
When two bashes proc at the same time on a melee hero they both deal damage and the longest stun duration is taken

True Strike

It's important to know that both Bash and Critical Strike are basically the same skill using different settings, Critical Strikes with a factor lower than 1.0x will not interfere with other Critical Strikes, and all Bashes have a factor of 0x by default (using 0x as a damage factor will make you deal 1x damage without the red number) , creating the interaction explained above. The ability True Strike from MKB is a good example of this, It uses the setting "Never miss" which makes it disregard evasion, blind and others,and it uses a 0x damage factor so it has no stacking issues with other Critical Strikes. True Strike will follow the "Bash" setting on the main table.

Bash and Crit Stacking

• Melee Unit: A melee unit has no problem having a crit and a bash in the same attack (it might even have more than one bash, as explained earlier)
• Ranged Unit: When a Critical Strike triggers in a ranged unit it will override all the previously acquired bashes and crits, if a Bash that was acquired after all the crit procs then it deals it's bonus damage and stuns normally (In this regard new Basher will always be considered the last acquired ability)