Cancellation is the term for removing magical charges and blessed/cursed status from an object or disabling the special attack of a monster. The most common source of cancellation is the wand of cancellation. A few are able to use the spellbook of cancellation. Magicbane can sometimes cancel things it hits. Foocubi can spontaneously become cancelled. Some potions can be transformed by dipping things in them, but this is not quite cancellation. Gremlins can also use their intrinsic-stealing attack to cancel other monsters.
Cancellation of objects
Cancellation has the following effects on objects:
- the object becomes uncursed
- the object's enchantment is set to +0 (applies to weapons, weapon-tools, and armor)
- all charges are removed from the object if it is magical (wands to (x:-1), magical tools to (x:0), rings to +0); non-magical tools, the wand of nothing, and the wand of cancellation do not lose charges
- scrolls and spellbooks (except the scroll of mail and spellbook of cancellation) are blanked
- most potions are converted to uncursed water
"In short, cancellation is quite thorough."
Except for certain scrolls, spellbooks, and potions, cancelled objects do not change type. Cancelling a bag of holding or magic lamp will merely uncurse it, not turn it into a sack or oil lamp. Cancelling an artifact will not turn it into a non-artifact. Cancellation has no effect on the objects inside a container.
Cancelled wands end up with (x:-1) charges, where x is its value prior to being cancelled. Cancelled wands can be recharged subject to normal restrictions on wand charging, but cannot be wrested; if they are zapped or engraved with, they will turn to dust.
Irina Rempt has written an excellent and thorough spoiler on cancelling objects. Consult it for more details.
If you zap a wand of cancellation at yourself, every item in your inventory (except the wand itself) will become cancelled. All equipment will revert to uncursed and +0, all spellbooks and scrolls will turn blank, etc. This affects only items, i. e. the naked player monster is not cancelled. Do not do this with a wand that you think is a wand of make invisible. Self-cancellation is one means of removing cursed gear; just be sure to drop or bag everything else before zapping. Polymorphed players revert, unless unchanging.
A corner case: You are immune to cancellation if you have magic resistance, unless you are zapping yourself. Monsters cannot zap cancellation in Vanilla, so this matters only for the point of maximum power you lose when hit by Magicbane (and unpolymorphing).
Cancellation of monsters
Monsters have an opportunity to resist cancellation effects. If the monster fails, it is cancelled and loses most of its special abilities.
Abilities stopped by cancellation
The following attacks and special abilities are entirely stopped by cancellation:
- Everything magic cancellation protects against, and passive versions of the same:
- Fire (e.g. fire ant burning attack)
- Cold (e.g. winter wolf breath)
- Shock (e.g. electric eel bite)
- Sleep (e.g. homunculus bite)
- Poison (e.g. killer bee sting)
- Paralysis (e.g. guardian naga bite)
- Drain life (e.g. vampire bite)
- Sticky attack (e.g. large mimic bite)
- Lycanthropy (e.g. the werejackal bite when it is in animal form)
- Slowing attack (e.g. Shade touch)
- Teleport by the quantum mechanic claw
- Sliming by the green slime touch
- Disenchanting by the disenchanter claw
- Power draining by the energy vortex
- Constitution draining poison by the rabid rat bite
- Dexterity draining poison by the quasit claw
- Gaze attacks
- Breath attacks (e.g. dragons)
- Erosion attacks (rusting, corroding and rotting) and passive erosion effects
- Drowning attacks (cancellation will prevent a sea monster from swinging itself around you, but if it is already holding you cancellation will not prevent drowning)
- Blinding attacks by light (e.g. yellow light)
- Confusion attacks (e.g. Yeenoghu)
- Stunning attacks
- Petrification attacks
- Acid attacks
- Seduction of succubi and incubi (by attack or #chat)
- Leprechaun gold stealing
- Nymph item stealing
- Gremlin intrinsic-stealing
- Xan leg attack
- Nurse healing attack
- Dividing of puddings
- Exploding attacks of spheres and lights
- Mimicking ability of mimics
- Spitting attacks (e.g. cobras)
- Summoning abilities of some demons and lycanthropes
- Coyote funny names
Cancelling clay golems causes them to be destroyed immediately (this is because they, according to legend, are animated by an inscription on their forehead, which the wand erases).
Abilities not stopped by cancellation
Some attacks which are not magical in nature cannot be cancelled, these include:
- the special attacks of the Riders (disease for Pestilence, hunger for Famine and touch of death for Death)
- the blinding attack of ravens
- a mind flayer's brain attack
- the passive attacks of the Oracle
- passive acid splashing
- Grabbing attacks (e.g. an owlbear's hug)
- Juiblex's disease attack
- The Wizard of Yendor's amulet stealing
- corpses of Trolls and the Riders returning to life
Cancelling Medusa removes her stoning gaze, which also means that she cannot be stoned with a reflecting item. Similarly, cancelling a floating eye means it cannot be paralyzed by its reflection.
It is possible to un-cancel most monsters by stoning them and then casting stone to flesh on their statue. This does not work on a foocubus or a nymph, though. Also, some monsters resist stoning, and tiny-sized monsters can turn into rocks or meatballs in the process. You can also un-cancel most monsters if they die and leave a corpse. Zap the corpse with a wand of undead turning - it will come back to life uncancelled.
Cancelling the floor
- "The engraving on the <floor> vanishes!"
Considering when to cancel
Suppose you need some blank scrolls and spellbooks and some potions of water, because you plan to use your magic marker and make holy water. If you have a wand of cancellation, one strategy is to put all your junk scrolls, spellbooks, and potions into one pile, then zap it with only one charge. However, it is usually easier to wet those kinds of items rather than cancelling them. The advantage of cancelling in the early game is that you do not need to use fountains, which are sometimes rare, and can cause nasty side effects. Once you find a pool or moat, or break a fountain to make a pool, you can save cancellation for use against monsters.
A few items can be rendered useful by cancelling them: a perfectly useless cursed -5 pair of levitation boots, for example, will cancel to a perfectly good uncursed +0 pair.
Cancellation is usually the only way to uncurse a cursed bag of holding without any drawbacks. If it is cursed, its weight is multiplied by 2; so if a player with a well filled blessed bag of holding dies, the bones file may contain a cursed bag of holding with 8 times the weight it had in the previous game. This will probably make it too heavy for you to be able to pick it up and uncurse it, even if you have maximized your carrying capacity and are carrying no other items. You can still loot or tip it, but if you do this, every item in the bag has a 1/13 chance of vanishing. The best tactic is to pick up anything from the bones pile that can be damaged by cancellation (especially wands, because their beatitude is mostly irrelevant anyway), and cancel the remaining items. The contents of the bag, just like with any other container, will not be cancelled.
If you are wielding a cursed two-handed weapon in Gehennom, you may have problems uncursing it if your scrolls of remove curse and holy water are all stored in containers (which you cannot open), because neither prayer nor spellcasting is possible in that state. If you cannot leave Gehennom without lifting the curse (e.g. because you have no free hands to gain levitation for Jubilex' lair), you may have to resort to dropping everything you can, then cancelling yourself. This will also cancel all the rest of your worn equipment, and so is only recommended in emergencies. (Some players drop potions of holy water in strategic places as a preventive measure.) NetHack 3.6.0 has added the tip command precisely to deal with such emergencies.