Arcane spell failure

Arcane Spell Failure

Arcane Spell Failure (ASF) is the chance that an arcane spell — that is, one from the Sorcerer/Wizard spell list or Bard spell list — will fail to be cast due to interference from the caster's armor or shield.

Such a failure expends the spell's spell points and cooldown as if it had been cast.

The ASF penalty from armor and shields is cumulative - they are added together.

Casting a spell from a wand is not subject to ASF, but reading a scroll is.

Spells that don't have a somatic component are not subject to ASF, either when cast or read from scrolls.

Scrolls and Arcane Spell Failure

Any scroll of a spell on the Sorcerer/Wizard spell list will be susceptible to "Arcane" Spell Failure even if the reader should not be subject to it - ie the reader is an Artificer, Bard wearing light armor, divine caster, etc. Thus, for example, Clerics cannot reliably use Protection from Energy scrolls in their heavy armor. This behavior may be modified in the future, as developers have acknowledged it should not work this way.

Similar to divine spells, Artificer-exclusive spells are not subject to Arcane Spell Failure, but Artificers using Sorcerer/Wizard list scrolls are subject to Arcane Spell Failure. So, for example, anyone using a Lightning Motes scroll will suffer no Arcane Spell Failure, but an Artificer is susceptible to Arcane Spell Failure when using a scroll of Reconstruct (available to Artificer but from the Sorcerer/Wizard spell list).

Similarly, Bards wearing light armor using scrolls on the Sorcerer/Wizard's list will be susceptible to Arcane Spell Failure even for spells also on the Bard spell list. A Bard wearing light armor has no chance of Arcane Spell Failure when casting Greater Heroism as a spell, but is susceptible to failure when casting it from a scroll.

Reducing Arcane Spell Failure

Item Enhancements

Item enhancements do not stack unless otherwise noted. Only the highest reduction will apply.

• The Lesser Arcane Casting Dexterity/Arcane Casting Dexterity prefix reduces ASF by 5%/10%. Arcane Casting Dexterity reduces total ASF, and as such can be on any item rather than needing to be on the armor or shield that's causing ASF.
• A Sapphire of Spell Agility +5/+10/+15 in a Blue Augment SlotBlue Augments
  • Natural Armor Bonus to AC: +1 to +7
  • Protection (deflection bonus to AC): +1 to +7
  • Resistance bonus to saves: +1 to +7
  • Physical Resistance Rating bonus: +2 to +14
  • Fortification: Light to Heavy (ML8)
  • Hit points (False Life): +5 to +35
  • Good Luck: +1 (ML12) +2 (ML20)
  • Armor Max Dex Bonus: +1 (ML12), +2 (ML20)
  • ASF reduction: 5%/10%/15% (ML12/16/20)
  Colorless Augments
  • Enhancement bonus to one ability: +1 to +7
  • Exceptional bonus to one ability: +1
  • Insight bonus to one ability: +2
  reduces ASF by 5%/10%/15%. This reduces total ASF, and as such can be on any item rather than needing to be on the armor or shield that's causing ASF.
• Lesser Arcane Sigil and Arcane Sigil are normally docent-exclusive enhancements, but can be added to Dragontouched Armor via the appropriate runes. They reduce ASF by 5% and 10% respectively. Prior to U17 LAS/AS were untyped and stacked with normal item enhancement effects and with each other. After U17, LAS/AS were apparently changed to global enhancement bonuses and no longer stack with other item enhancements or with each other. [1]
• Twilight reduces ASF by 10%, and Greater Twilight reduces ASF by 20%. Twilight affects the armor or shield it is on only, however. It is applied before effects granting global reduction of arcane spell failure and stacks with them.

Armor/Shield Materials

• Mithral is exceptionally light, reducing the Arcane Spell Failure chance of an armor or shield made with it by 10%. For very light types of armor or shields, this can completely negate ASF by itself.
• Darkleaf reduces the ASF of the armor or shield made with it by 5%, but this material is generally found on rather heavy armors (Breastplate and Banded) and will not negate ASF alone.
• Alchemical Crystal reduces the ASF of an Alchemical Shield by 10% when applied to it through reforging.

Elven Arcane Fluidity

• The Elven Arcane Fluidity I/II/III/IV enhancements are available to Elves and Half-Elves at level 2/6/10/14 at a cost of 1/2/3/4 AP. Drow have access to Elven Arcane Fluidity I/II/III but not IV. Each rank replaces the previous - they are not cumulative.
  • Elven Arcane Fluidity I reduces ASF by 5% on Light armor only.
  • Elven Arcane Fluidity II reduces ASF by 10% on Light armor or 5% on Medium armor.
  • Elven Arcane Fluidity III reduces ASF 15% on Light armor, 10% on Medium armor, and 5% on Heavy armor or shields.
  • Elven Arcane Fluidity IV reduces ASF 20% on Light armor, 15% on Medium armor, and 10% on Heavy armor or shields.

Warforged

Arcane Spell Failure is of particular importance to Warforged arcane casters as their natural body plating imposes at least a 5% ASF penalty by default.

• The default Composite Plating imposes 5% ASF, while the optional Mithral Body imposes 15% and Adamantine Body imposes 35%.

Fortunately, there are also warforged-exclusive ways to mitigate ASF:

• Composite and Mithral body plating are considered light armor and thus don't impact warforged Bards.
• The Warforged Inscribed Armor I/II/III enhancements are available to warforged at level 2/6/10, reducing ASF from body plating by 5%/10%/15%.
• Lesser Arcane Sigil and Arcane Sigil are docent-exclusive enhancements, reducing ASF by 5% and 10% respectively. Prior to U17 LAS/AS were untyped and stacked with normal item enhancement effects and with each other. After U17, LAS/AS were apparently changed to global enhancement bonuses and no longer stack with other item enhancements or with each other. [2]

Bards

• As noted above, bards are not subject to ASF while wearing Light armor.
• The Warchanter II bard PRE extends this benefit to Medium armor as well.

Artificers

• Artificers are not normally subject to ASF.
• However, the Battle Engineer I artificer PRE grants a 10% reduction in ASF from armor. This is generally only useful when using Scrolls subject to ASF as above.
• Bug: Battle Engineer I is currently bugged and does not grant the -10% ASF reduction. [3]

Default ASF Penalties

Table: Arcane Spell Failure — Armor
Armor Name	Failure %	Armor Type
Composite Plating (Warforged only)	5%	Light
Padded Armor	5%	Light
Leather Armor	10%	Light
Mithral Body (Warforged only)	15%	Light
Studded Leather Armor	15%	Light
Chain Shirt	20%	Light
Hide Armor	20%	Medium
Breastplate	25%	Medium
Brigandine	25%	Medium
Scalemail	25%	Medium
Chainmail	30%	Medium
Adamantine Body (Warforged only)	35%	Heavy
Banded Mail	35%	Heavy
Full Plate	35%	Heavy
Half Plate	40%	Heavy
Splint Mail	40%	Heavy

Table: Arcane Spell Failure — Shields
Shield Name	Failure %
Buckler	0%
Light Shield	5%
Heavy Shield	15%
Tower Shield	50%