Magic cancellation

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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 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 in this article referred to as special melee attacks. A precise list of the special melee attacks that magic cancellation protects against is provided in the section below.

A player is protected from special melee attacks 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 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.

What magic cancellation protects againstEdit

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 some types of armor covered your entire body surface, so the attacker effectively cannot touch you despite his successful attack. The fact only cloaks grant the highest level of protection still reflects this. 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
• Note 1: Magic cancellation protects against special melee weapon attacks, such as level drain from a barrow wight's weapon, but it does not protect against weapons that are thrown or launched, such as poisoned arrows and daggers.
• Note 2: The type of 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 3: Disenchantment by the by the disenchanter claw is prevented, but magic cancellation does not protect against the passive disenchanting attack, since passive attacks are listed in the leftmost column "Attack type unaffected".
• Note 4: 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.

How the protection worksEdit

Magic cancellation protects the player by reducing the probability of special melee attacks occurring.

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%

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.

Magic cancellation is very useful, as can be seen from the following example. If you are wearing one of the best armors in the game, the gray dragon scale mail, you are are attacked by a vampire, then 1/3 of the vampire's successful bites cause you to lose a level. If however you wear an easy-to-find orcish cloak (MC 2) over the armor, the probability of the vampire's bites causing level drain will drop to $\frac{1}{3}\times\frac{52}{150}\approx 11.6\%$. An even better magic cancellation, such as that of an oilskin cloak (MC 3), would reduce the probability to $\frac{1}{3}\times\frac{3}{150}\approx 0.7 \%$.

Magic cancellation numbers of armorsEdit

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
mummy wrapping cloak
orcish chain mail body armor
orcish ring mail body armor
leather cloak cloak
splint mail body armor
studded leather armor body armor
cloak of displacement cloak 2
cloak of invisibility cloak
cornuthaum helmet
crystal plate mail body armor
dwarvish cloak cloak
orcish cloak cloak
plate mail body armor
cloak of protection cloak 3
cloak of magic resistance cloak
dwarvish mithril-coat body armor
elven cloak cloak
elven mithril-coat body armor
oilskin cloak cloak
robe cloak

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

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. It is important to remember that cloaks of magic resistance also provide the highest level of magic cancellation.

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.

StrategyEdit

Magic cancellation is a high priority trait. In the early game, although orcish- and dwarvish cloaks have no effect on AC, they both confer MC 2, which protects against roughly two thirds of special melee attacks. This makes them useful until mithril-coats and the rarer MC 3 cloaks are found. Most players strive to have maximum magic cancellation (MC 3), but some favour the benefits conferred by a cloak of displacement (MC 2), while wearing dragon scale mail (MC 0).