Effect stacking

Non-stacking redirects here. For other uses, see stack.

Effect stacking refers to the combined impact on a single effect from multiple sources, including equipment, skills, and environment. Typically, effects stack by adding the totals from all sources, however some effects are capped, some sources have their contribution capped, and other effects might combine under a more complex formula.

Types of stacking

Equipment bonuses

All bonuses on weapons stack. However, weapon bonuses to armor rating are limited by a shared cap (see below), unless that bonus is from an inscription.

Bonuses on armor generally stack, but sometimes in unintuitive ways:

"Non-stacking" armor upgrades

Some effects of runes and insignias are labeled as (Non-stacking). This is a bit of a misnomer. Effects labeled as non-stacking don't stack with each other, but still stack with other effects.

• For example, the elementalist runes of Major and Superior Air Magic both list their attribute bonus as (Non-stacking). An elementalist equipped with both will receive only the greater bonus of +3 Air Magic, not a combined +5.
  • This "non-stacking" bonus will, however, stack with other sources of Air Magic that aren't labeled as non-stacking, such as the Storm Eye headpiece or the Glyph of Elemental Power.
  • Note that only the attribute bonuses of these runes are labeled as non-stacking, not the health penalties. Both penalties apply to the elementalist, for a total of 110 health lost.
• For another example, a Rune of Clarity reduces the duration of both Blindness and Weakness on you by 20%; both effects are non-stacking. Equipping a second Rune of Clarity won't reduce blindness duration any further, but equipping a shield with the "I Can See Clearly Now" inscription or summoning a spirit of Recovery will.

"Local" armor effects

Armor rating and damage reduction from insignias, as well as the inherent armor rating of each armor piece, only apply when that specific body part is hit and don't affect other armor pieces.

• For example, if your headpiece has an armor rating of 60 and your other armor pieces have armor ratings of 45, you don't have a combined armor rating of 240. You have an armor rating of 60 against hits to your head and 45 against all other hits.
• For another example, if you upgrade all of your armor pieces with Blessed insignias, which provide +10 armor rating while enchanted, and you are enchanted, your armor rating isn't increased by +50. Rather, your armor rating is consistently increased by +10, regardless of where you are hit.

Skill effects

Most skill effects do not stack — the most recent or the most powerful application takes precedence.

Effects that stack

• The beneficial effects of hex spells on different targets stack.
  • Life Siphon cast on two foes will provide twice as much health regeneration to the spellcaster compared to only one Life Siphon.
• The beneficial effects of hex spells on the same target stack.
  • Assassin's Promise provides each spellcaster the energy gain and skill recharge when the foe dies.

Effects that do not stack

• Some skills will not stack with others of the same type: a character can only be affected by one stance, one preparation, one party bonus, one glyph, one weapon spell, and one form at a time. Activating a new one of the same type will override any existing ones.
• Animal companions can only be under the effects of a single Pet Attack buff.
• Characters can only hold one bundle at a time, so each new casting of an Item Spell causes the first urn to be dropped (triggering the when dropped effects).
• Armor rating bonuses from all skills are capped to a maximum of 25, however there are several bugs associated with this.
• Each Binding Ritual will result in the death of any allied spirit of the same type. Similarly, Nature Rituals will kill existing allied and enemy spirits of the same type.

Non-additive stacking

• Random chances stack multiplicatively rather than additively. For example, a character enchanted with both Aegis and Guardian (each giving 50% block chance) will have a 75% chance to block rather than a 100% chance.
• Attack speed and movement speed stack multiplicatively. For example, a character affected by Flail and "Fall Back!" will have 89.1% movement speed rather than 100%.
• Percentage modifiers stacking multiplicatively tend to be the rule rather than the exception (for example: healing, adrenaline gain, recharge time, and damage multipliers also).

Effect caps

The game limits the maximum bonus or penalty that can be accrued from multiple sources; the effects stack, but only to a specified amount. In most cases, this cap can be exceeded by a single source.

Property	Positive	Negative	Notes
Attack speed	+33%	-50%	Specific implementation details distort the potency of this modification. Actually, attack speed bonuses cause up to +49% more or -33% fewer attacks.
Movement speed	+34%	-50%
Chance to block or miss	100%		Stacks multiplicatively. There are effects that prevent blocking or missing, but none that reduce the chances to block or miss.
Healing		-40%	Stacks multiplicatively.
Adrenaline gain	+100%	-50%
Health or energy regeneration	+10	-10	These caps also apply to single effects (not just multiple sources).
Recharge time		-50%	A single skill's effect can bypass this limit; item mods cannot stack beyond this limit.
Activation time	+150%	-25%	Fast Casting does not count toward this cap.
Armor rating	+25	60 AR	The positive cap is only applied to bonus armor. Core and special armor are uncapped. Negative bonus armor can only reduce your armor to 60, or to your core armor rating if that is below 60. See armor calculation for the full formulas.
Attribute	20	0	These caps also apply to single effects (not just multiple sources). 21 can be reached using weapons with a chance of boosting an attribute.
Damage multipliers
Projectile travel-speed	+100%	-50%
Maximum health		1	The minimum cap also apply to single effects (not just multiple sources).
Condition duration		0s	The cap only applies to the remaining duration; conditions can be re-applied indefinitely (although there is some evidence that suggests this is capped at 12 hours, on a practical level, there is no maximum). A zero-second duration condition will trigger Fragility only once (not twice, as expectable if it was on application and on end).
Combat experience	350%

Notes

• The maximum number of maintained enchantments is limited only by your energy regeneration; you can never have your net energy regeneration at less than -10 (any maintained enchantments in excess of that cap will be lost). For example, a Monk can maintain a maximum of 14 enchantments.