When spellcasting the Fail column appears in the menu which occurs when using the [Z] command.

To calculate spell failure, you first need to sum together the penalties marked with a number sign (#) below. An increasing total penalty is worse for spellcasting, and is limited to a maximum of 20.

  • The "BASE" value from the table below, depending on the character's class.
  • If an "emergency" spell (noted with a + above), the "EMERG" field.
  • If wearing any shield, the amount in the "SHIELD" field.
  • If wearing metallic body armor, the amount in the "SUIT" field.
  • If also wearing a robe, only add half the amount (rounded down).
  • If wearing a robe without metallic armour, subtract the amount in the "SUIT" field.
  • If wearing a metallic helmet other than the helm of brilliance, add 4.(Metal helmets interfere with the mind.)
  • Metallic gloves add 6 (casting channels through the hands).
  • Metallic boots add 2 (all metal interferes to some degree).
  • Subtract 4 if the spell is special to that class (see table).
Arc      5#      0#      2#     10#    Int     Magic mapping
Bar     14#      0#      0#      8#    Int     Haste self
Cav     12#      0#      1#      8#    Int     Dig
Hea      3#     -3#      2#     10#    Wis     Cure sickness
Kni      8#     -2#      0#      9#    Wis     Turn undead
Mon      8#     -2#      2#     20#    Wis     Restore ability
Pri      3#     -2#      2#     10#    Wis     Remove curse
Ran      9#      2#      1#     10#    Int     Invisibility
Rog      8#      0#      1#      9#    Int     Detect treasure
Sam     10#      0#      0#      8#    Int     Clairvoyance
Tou      5#      1#      2#     10#    Int     Charm monster
Val     10#     -2#      0#      9#    Wis     Cone of cold
Wiz      1#      0#      3#     10#    Int     Magic missile

Next, calculate a base chance of success, which is 5.5 times your intelligence or wisdom STAT, depending on your class. This chance is modified by the following factors:

  • SKILL level (Unskilled = 0, Basic = 1, Skilled = 2, Expert = 3)
  • spell level (LVL)
  • experience level (XL)

according to this formula:

difficulty = (LVL * 4) - (SKILL * 6) - (XL/3) - 5

If this is positive, your chance is reduced according to another formula:

chance = base chance - square root of ((900 * difficulty) + 2000)

If it is negative, it will be increased with diminishing returns: the absolute value is multiplied by (15/LVL), capped at 20, and added to the base chance.

The resulting chance is clipped to the range of 0% to 120% success. If you are wearing a shield larger than a small shield, the chance is then reduced to 1/4 its amount (except if it is the special spell for your class -- then it is only halved).

Finally, the chance of success is adjusted by your total penalty using the following formula:

chance = (chance * (20-penalty) / 15) - penalty

The result is clipped to the range of 0% to 100% success.

This page is based on a spoiler by Dylan O'Donnell. The original license is:

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