Magic cancellation

For the effects of a wand of cancellation or a spell of cancellation, see Cancellation.

Magic cancellation, or, shortly, MC, is a property of some pieces of armor which protects against a wide variety of special melee attacks by monsters, such as poisonous killer bee stings and lycanthropy caused by werejackal bites. A precise list of attacks that magic cancellation protects against is provided in the section below. Generally speaking, magic cancellation protects against special non-damage effects (such as sliming) caused by a monster attacking and touching the player with some part of its body.

A player is protected by an aura of magic cancellation if one of the pieces of armor worn has magic cancellation. Each piece of armor has a magic cancellation number (MC number) ranging from 0 to 3, where 0 is the lowest (worst) and 3 is the highest (best). Note that magic cancellation is not cumulative — the player's magic cancellation is the maximum of that provided by any single piece of armour worn. This means that if you are wearing a chain mail with MC 1, and a dwarvish cloak with MC 2, then your magic cancellation is 2. Having the highest (best) magic cancellation means that only 1/50 of special, non-damage body-to-body melee attacks will succeed (assuming they would hit otherwise). This makes magic cancellation a high priority trait.

How it works

Understanding how magic cancellation works requires understanding of how a 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.

Attack type		Damage type
Attack type unaffected	Attack type prevented	Damage type prevented	Damage type unaffected
Passive attacks Spitting attacks Engulfing attacks Breath attacks Explosions from proximity Explosions from dying Gaze attacks Magic spells	Claw Bite Kick (note 1) Head butt (note 1) Touch Sting Tentacle attack (note 1) Grabbing attacks (note 1) Weapon attacks	Fire Cold Shock Sleep Poison Paralysis Drain life Sticky attack Lycanthropy Slowing attack Teleport Sliming Disenchanting Dexterity draining poison Power draining	Ordinary physical damage Magic missile damage Disintegration effects Acid damage Blinding effects Stunning effects Leg damage by Xans Petrification effects Gold stealing effects by leprechaun Item stealing effects Erosion effects (including rusting, corroding and rotting) Confusion effects Digestion damage Healing effects by nurses Drowning effects Intelligence drain effects by mind flayer Disease effect by Juiblex Seduction effects Hallucination effects Amulet stealing effects by the Wizard of Yendor Intrinsic-stealing effects by gremlins Random clerical spell effects, magic spell effects or breath weapon effects Special damage effects of the Riders
	Examples
	Fire damage from a fire ant bite Cold damage from a lich touch Shock damage from an electric eel bite Sleep caused by a homunculus bite Poison damage from a killer bee sting Paralysis caused by a guardian naga bite Drain life by a barrow wight weapon attack Sticking-to caused by a large mimic bite Lycanthropy caused by werejackal bite when it is in animal form Slowing caused by the Shade touch Teleport caused by the quantum mechanic claw Sliming caused by the green slime touch Disenchanting by the disenchanter claw (note 2) Constitution draining poison by the rabid rat bite Dexterity draining poison by the quasit claw Power draining by the energy vortex (note 3)
Note 1: The actual damage done by every signle kick, headbutt, tentacle attack, and grabbing attacks in the game are listed in the rightmost column "Damage type unaffected". And hence they all bypass magic cancellation. Note 2: It does not however protect against the passive disenchanting attack, since passive attacks are listed in the leftmost column "Attack type unaffected". Note 3: Interestingly, the attack type is engulf, which is listed as an attack affected by magic cancellation. This may be a bug in the source code.)

List of magic cancellation numbers by armor

The relationship between magic cancellation level and chance of a body-to-body magical attack success is as follows:

Magic cancellation number	Chance of attack succeeding
Magic Cancellation 0	$\frac{150}{150}$, i.e. 100%
Magic Cancellation 1	$\frac{101}{150}$, i.e. ~67%
Magic Cancellation 2	$\frac{52}{150}$, i.e. ~35%
Magic Cancellation 3	$\frac{3}{150}$, i.e. 2%

All cloaks, some pieces of body armor, and the cornuthaum provide non-zero magic cancellation. All other items in the game provide zero magic cancellation. The following list contains all the pieces of armor with non-zero magic cancellation:

Armor name	Armor type	Magic cancellation number
alchemy smock	cloak	1
chain mail	body armor	1
mummy wrapping	cloak	1
orcish chain mail	body armor	1
orcish ring mail	body armor	1
leather cloak	cloak	1
splint mail	body armor	1
studded leather armor	body armor	1
cloak of displacement	cloak	2
cloak of invisibility	cloak	2
cornuthaum	helmet	2
crystal plate mail	body armor	2
dwarvish cloak	cloak	2
orcish cloak	cloak	2
plate mail	body armor	2
cloak of protection	cloak	3
cloak of magic resistance	cloak	3
dwarvish mithril-coat	body armor	3
elven cloak	cloak	3
elven mithril-coat	body armor	3
oilskin cloak	cloak	3
robe	cloak	3

Most players like to have maximum magic cancellation, but some favour the benefits conferred by a cloak of displacement (MC 2).

Difference between magic cancellation, cancelling a monster, and magic resistance

Magic cancellation is a property of armor that reduces the probability of certain special monster melee attacks of succeeding. A monster can also be cancelled by zapping a wand or a spell of cancellation. This is somewhat different from magic 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 though magic cancellation. See the article on cancellation to compare effects.

Magic cancellation is not the same as magic resistance. Magic resistance is an extrinsic that protects against spell, wand, and trap effects and damage.

Common misconceptions

• 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 disenchanters passive attack.
• Magic cancellation does not protect against the hissing attack of the cockatrice.

References

• Source:Mhitu.c
• Source:Monattk.h

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