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.

Magic cancellation must not be confused with cancellation caused by a wand or spell, nor with magic resistance. See section Difference between magic cancellation, cancelling a monster, and magic resistance for further details.

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. 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 protects 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.

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 or constitution draining poison Power draining	Ordinary physical Magic missile Disintegration Acid Blinding Stunning Leg damage by Xans Petrification Gold stealing effects by leprechaun Item stealing Erosion (including rusting, corroding and rotting) Confusion Digestion Healing effects by nurses Drowning Intelligence drain Disease effect by Juiblex Seduction Hallucination Amulet stealing by the Wizard of Yendor Intrinsic-stealing eby gremlins Random clerical spell, magic spellor breath weapon damage Special damage of the Riders
Examples — unaffected due to attack type	Examples — prevented due to combination of attack type and damage type.		Examples — unaffected due to damage type
Floating eye passive paralysis attack Disenchanter passive disenchanting attack Guardian naga spitting poison Ice vortex engulfing cold Red dragon fire breath Yellow light blinding explosion Medusa petrifying gaze Pyrolisk fire gaze Lich magic spells	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)		Physical damage due to tiger claws Medusa petrifying gaze Raven blinding claws Seduction due to succubus bites Intelligence drain due to mind flayer tentacle attacks Purple worm engulfing digestion Drowning due to giant eel wrapping Hallucination caused by a black light exploding Erosion due to brown pudding bites Nymph stealing claw
Note 1: The actual damage done by every single 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: This is an exception to the general principles for magic cancellation. The power draining by the energy vortex is prevented by magic cancellation, despite the attack type being engulf, which is listed in the leftmost column as an attack unnaffected by magic cancellation. This may be due to a bug or omission in the source code.)

List of magic cancellation numbers by armor

The relationship between magic cancellation number and chance of a body-to-body special attacks 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 strive 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.
• 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.

References

• Source:Mhitu.c
• Source:Monattk.h
• armr-343.txt

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