Miscast effect

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Version 0.25: This article may not be up to date for the latest stable release of Crawl.

A miscast effect occurs when a player fails to cast a spell successfully. These can range in severity from completely harmless to inflicting heavy damage and magic contamination, depending on the school of magic, the spell level, and the degree of failure. Players wishing to protect themselves from miscasts should focus on increasing the spell success rate, as this reduces both the frequency and intensity of miscasts. Additionally, miscasts from some schools of magic produce elemental damage that can be resisted.

The in game spell failure rate color indicates the maximum potential damage relative to your current max HP. These are calculated as if the damage is irresistible, even for those schools whose miscast effects are resistible or not directly damaging.

Color Potential
HP Loss
Grey None safe
White 0% - 10% slightly dangerous
Yellow 10% - 30% dangerous
Light red 30% - 50% quite dangerous
Red 50% - 70% extremely dangerous
Purple 70% - 100% potentially lethal

The spell description shows the full list of possible miscast effects, including maximum damage and damage types.


Miscasting a spell from any school causes contamination based on the spell level and degree of failure (which can range from 1 to 99 for spells that are almost impossible to cast; higher success rate reduces the maximum range):

Contamination: (Spell Level × Spell Level × Degree of Failure + 250) / 500

If this results in more than 0.8 points of contamination, an additional effect is applied based on the spell school. If the spell has multiple schools, one of them is chosen at random. The intensity of the effect is rolled based on the spell level and the raw spell failure chance (an internal value from 1 to 99, not the failure rate shown on the spell list).

Intensity: (Spell Level)d(Spell Level + Raw Failure Rate) / 9

For damaging effects, this is the amount of damage done. For status effects (slow and dimension anchor), this is the duration in turns. Other effects as listed:

School Effect
Air Magic electricity damage
Conjurations irresistible damage
Earth Magic shrapnel damage
(reduced by AC three times)
Hexes debuff and slow
Charms debuff and slow
Fire Magic fire damage
Ice magic cold damage
Necromancy draining damage
Poison Magic poison damage
Summonings durably summoned nameless horror
HD = 2 × Intensity / 3
Translocations Dimension Anchor
Transmutations double current contamination
plus 9 × Intensity / 1000 contamination

Hell effects

Hell's mystical force selects a miscast or other effect with the probabilities given below. These miscasts only apply the school effect, not the initial contamination. There is a special case if the miscast effect spawns any monsters: those monsters are not summons and are worth experience.

See Also

Magic contamination


  • Prior to 0.25, the miscast effect system was significantly more complicated, with three different types of effects per school, depending on the severity of the miscast.
  • In 0.16, many magic miscast effects received a significant overhaul.
  • Prior to 0.14, Hell's mystical force could paralyze the player.
  • Prior to 0.13, Zot traps inflicted a random severity 3 miscast, instead of having a hardcoded list of effects.