Magic cancellation, or MC for short, is a property which protects the player from certain non-damage effects caused by a monster attacking and touching the player with some part of its body. Examples include poison from killer bee stings, lycanthropy caused by werejackal bites, and the green slime's sliming attacks. Such attacks are referred to as special melee attacks in this article. Having the highest (best) magic cancellation means that only 1⁄10 of special melee attacks will succeed (assuming they would hit otherwise). This makes magic cancellation a high priority trait. A precise list of the special melee attacks that magic cancellation protects against is provided in the section below.
Magic cancellation must not be confused with cancellation caused by a wand or spell, nor with magic resistance. See § Differences from cancellation and magic resistance for further details.
Your current level of magic cancellation can be verified via any source of enlightenment; "You are warded" means you have MC1, "You are guarded" is MC2, and "You are protected" is MC3.
The most common source of magic cancellation is armor. Each piece of armor has a magic cancellation number (MC number) ranging from 0 (worst) to 3 (best). Note that magic cancellation from armor is not cumulative—the player's magic cancellation is the maximum of that provided by any single piece of armor worn. This means that if you are wearing a chain mail with MC 1, and a dwarvish cloak with MC 1, then your magic cancellation is still 1.
Magic cancellation can also be granted by protection, either intrinsic or extrinsic. Extrinsic protection augments your magic cancellation by 1, to a maximum of 3. Intrinsic protection counts as magic cancellation 1, but doesn't stack with armor sources. The sources of extrinsic protection are the ring of protection, the Tsurugi of Muramasa, and the Mitre of Holiness; more than one such source provides no additional benefit. Intrinsic protection is granted when you get an AC bonus by donating to an aligned priest or by a favor when praying. Intrinsic protection may be lost by a gremlin's special attack or eating a disenchanter corpse; if so, donating the appropriate amount to an aligned priest will restore it, even if it would fail to improve your AC. High priests have extrinsic protection, and aligned priests and monsters represented by A have intrinsic protection.
The following list contains all the sources of magic cancellation:
|Armor name||Armor type||Magic cancellation number|
|Extrinsic protection||N/A||+1 (max 3)|
|cloak of displacement|
|cloak of invisibility|
|cloak of magic resistance|
|banded mail||body armor|
|bronze plate mail|
|orcish chain mail|
|orcish ring mail|
|studded leather armor|
|crystal plate mail||body armor|
|cloak of protection||cloak||3|
Magic cancellation protects the player by reducing the probability of special melee attacks occurring.
- The attack must first hit the player. This means passing the player's armor class. Unless you are resistant to the damage type of the attack, you will be dealt damage, which reduces your hitpoints. This occurs regardless of whether the damage type was ordinary physical, or a special type such as poison.
- After this, there is a probability of special effects occurring, for instance:
- The monster itself must not be cancelled.
- Finally, the attack must pass the player's magic cancellation aura. The chance of this happening is 1 − 0.3×MC, or listed in the table below:
|Magic cancellation number||Chance of attack succeeding|
If all these tests are passed, the player will suffer the special effect. In the case of fire, cold, and shock, there is further a test for determining if any inventory items are damaged or destroyed.
Understanding how magic cancellation works requires some understanding of how an attack works in NetHack. An attack has two characteristics: attack type (e.g. bites and stings) and damage type (e.g. physical or poisonous). A soldier ant, for instance, has two attacks: a bite which does 2d4 physical damage (i.e. ordinary damage), and a sting which does 3d4 poison damage. Magic cancellation will not protect against the 2d4 physical damage from the bite, nor will it prevent the 3d4 damage caused by the sting. It will, however, protect against the special effects from the poisonous sting, which randomly includes hitpoint reduction, attribute reduction, and instadeath.
There is no obvious pattern to what magic cancellation does and doesn't protect against. Shortly put, magic cancellation protects against certain attack types that deal a certain type of damage. This relation is shown in the table below. To be prevented by magic cancellation, both the attack type and damage type must be in the orange area of the table. If either the attack type or damage type is outside the orange area, magic cancellation will have no effect on the attack.
In earlier versions of the game, the idea was that some types of armor covered your entire body surface, so the attacker effectively could not touch you despite his successful attack. Over time, with the addition of the cornuthaum and many types of special attacks, this point has become moot, and the current explanation can only be "it's magic".
|Attack type||Damage type|
|Attack type unaffected||Attack type prevented||Damage type prevented||Damage type unaffected|
|Examples– unaffected due to attack type||Examples – prevented due to combination of attack type and damage type.||Examples – unaffected due to damage type|
Differences from cancellation and magic resistance
Magic cancellation is distinct from cancellation, which a monster suffers when hit by a wand or spell of cancellation. Cancelling a monster completely removes the monster's ability to perform its special melee attacks, while magic cancellation only reduces the probability of those attacks succeeding against the player. Also, the attacks affected by cancelling a monster are not exactly the same as those prevented through magic cancellation. See the article on cancellation to compare effects.
Also note that the magical cancellation is different from intrinsic resistances against fire, cold, and shock damage. If you suffer fire damage while fire resistant, you won't be dealt hit point damage, but there is still a chance of items such as scrolls, spellbooks, and potions being destroyed. Magic cancellation on the other hand won't prevent the damage, but it will reduce the probability of item-destroying effects occurring.
- Magic cancellation does not protect against paralyzing passive attacks nor gaze attacks, which include the attacks of floating eyes and Medusa.
- Magic cancellation partially protects against disenchanters; it prevents the disenchantment though the claws, but not through the disenchanter's passive attack.
- Magic cancellation does not protect against the touch nor against the hissing attack of the cockatrice. It is however possible to cancel the cockatrice itself, using a wand of cancellation or spell of cancellation. This will remove its ability to petrify by hissing only.
- Monsters, including pets, enjoy magic cancellation from armor just as the player does. This is especially important if you rely on a powerful pet, as monsters cannot gain intrinsic resistances from eating corpses.
Magic cancellation is a useful properly which gets more useful the more of it you have; a character with MC3 will suffer only 1⁄4 as many cancellable attacks as one with MC2. However, its value must be weighed against its opportunity costs. Acquiring MC3 requires a cloak of protection, or one of the MC2 cloaks or suits and a source of extrinsic protection. Armor which provides MC2 or 3 doesn't provide the useful properties of the MC1 magic cloaks or MC0 dragon scale mail. In many cases, it's better to wear the cloak of magic resistance to protect yourself from polymorph traps and death magic, or silver dragon scale mail to protect your wands and rings from lightning. Most cancellable attacks have either resistances to negate them, or countermeasures to reverse their effects (fire for sliming, holy water for lycanthropy, Elbereth to unstick from mimics), so a well-prepared player may find magic cancellation a lower priority than more critical properties.
Magic cancellation only protects from melee attacks, and characters with strong ranged attacks can generally kill the attackers from a distance before they become a threat. Beware of monsters (especially nasties) being summoned to you, though.
If you want MC3, you may want to treat the ring of protection as a situational item, which you equip when a relevant monster appears and then swap out for a more generally useful one when the situation is dealt with. Priests and Samurai get protection from their quest artifacts; other roles must be lawful (at least temporarily) to wish for them.
Before version 3.6.0, magic cancellation was more readily available and stronger, and intrinsic or extrinsic protection had no effect on it. For more details on magic cancellation as it functioned in 3.4.3, see Magic cancellation (3.4.3).
In Slash'EM Extended, a magic cancellation of 3 prevents attacks 75-90% of the time depending on the player's spirituality skill. Magic cancellation values greater than 3 are possible in that variant and give even better protection; the actual effectiveness can be seen here.