Is AcidFog.png
Acid Fog
Acid fog effect1.jpg
Spell Information
Spell level : Innate level: 6, Sorcerer/Wizard: 6, Other: Cleric with Destruction domain 6
School : Conjuration
Descriptor(s) : Acid
Components : Verbal and Somatic
Range : Long
Target/Area : Large
Duration : 1 round per 2 cLevels
Save : Fortitude partial
Spell resistance : Yes


Acid Fog creates a thick, clinging, greenish cloud. Creatures entering the cloud take 4d6 points of acid damage. Creatures entering the cloud must make a Acid-based Fortitude save or have their movement reduced by 50%. Every round a creature spends in the cloud, it suffers 2d6 points of acid damage.

Bug Notes[]

Edit Nov 8, 2010: Removed several wrong bug comments.

  • When a target affected by Movement Speed Decrease exits the Acid Fog area, the effect applied by Acid Fog is supposed to be removed. However, while checking for effects on the target applied by Acid Fog, the script is kicked out of the loop as soon as it finds the first effect applied by Acid Fog. This means, any further effects are left unchecked. If a spellcaster casts several Acid Fogs on the same target and the target always fails its saving throw, the Movement speed decrease effect is applied by each Acid Fog, but when the target leaves the area, only the first effect is removed, which means the movement speed decrease applied by second, third etc. Acid Fog cloud is still there and since the effect is permanent, the target is slowed permanently, which is not supposed to happen. The script must be allowed to loop through all effects on the target without interruption.
  • In terms of spell resistance checks, this AoE spell suffers from exactly the same bug as any other AoE spell (Cloudkill, Mind Fog etc.): Spell Penetration feats are ignored and caster level is not calculated properly for purposes of spell resistance penetration, so, for example a sorcerer 10/ Arcane scholar of Candledeep 10 caster with greater spell penetration feat seems to have an effective caster level of 10 (prestige class levels are ignored and greater spell penetration feat as well). This happens, because SR checks are not done directly between caster<->target, but filtered through the AoE. This hard-coded bug can be bypassed through scripting by moving the entire spell code to a separate function and performing the SR checks directly between the area creator and the target:

AssignCommand(GetAreaOfEffectCreator(),Resist(oTarget) );

  • This doesn't make use of the much better ApplyMetamagicVariableMods() function for doing metamagic effects in the heartbeat or enter scripts.

Gameplay Notes[]

In case the description isn't clear: The Fort Save only negates the slow movement, and it is only rolled when they enter the fog. Remaining in the fog after that does not trigger additional Fort saves. Also, creatures still take 4d6 damage on entering and 2d6 each round they remain, regardless of the Fort save.

Spell resistance acts as normal but, of course, due to its high level it eats up spell mantles (You are tested for its effects when you enter it and every round too).

The main reason for the Slow effect is to hamper movement out of the area, thus meaning the enemy takes more damage. This is a good spell to make an area inaccessible and control the battlefield with, or simply to force your enemy to fight inside it.

As most area of effect spells, if the caster is killed this spell should stop.

In the Mask of the Betrayer, acid fog can be used to create powerful acid enchantment to weapons. However, since Safiya is a Transmuter and cannot learn Conjuration spells, and Kaelyn does not have Destruction domain, the only person able to do this enchantment is the player him/herself.

Original Rules comparison[]

  • Spell resistance doesn't apply (like with most Conjuration spells)
  • No saving throw whatsoever.
  • Additional to hampered movement, the spell also causes hampered sight.
  • No initial 4d6 damage.
  • Lasts twice as long (1 round / level).


Acid fog spell in the casting phase.

Acid fog spell in the projectile phase.

Acid fog spell in the impact phase.

External resources[]