Potion of cancellation
|A potion which ends most magical effects, good or bad, affecting you.|
Quaffing a potion of cancellation immediately ends any of the following negative status effects you may be suffering from: confused, paralyzed, slow, silenced, petrifying/petrified, liquefying, sentinel's mark, Sap Magic, fire/poison vulnerability, dimension anchor, antimagic, and corona. It also removes some magical contamination, if you have any. (Note that you cannot quaff the potion if you are paralyzed or fully petrified, but technically these effects would also be removed by the potion, according to the code.)
It also cancels teleport control, imminent teleport, haste, swiftness, might, agility, brilliance, phase shift, invisible, stealth, darkness, repel missiles, deflect missiles, fire shield, icy armour, condensation shield, stoneskin, resistance, magic shield, shroud of golubria, confusing touch, sure blade, branded weapon, charged Delayed Fireball, Olgreb's Toxic Radiance, Portal Projectile, death channel, disjunction, and regeneration.
After one turn, the potion additionally cancels flight and all transformations not listed above.
Notably, it does not affect Death's Door, lowered MR, Quad Damage, Tornado, Infusion, Song of Slaying, the Elixir Card, Dragon's Call, Aura of Abjuration, or Powered By Death. It also ignores poison and liquid flames, berserk, sleeping, and fortitude, and god-specific effects. It has no effect on stat drain. It will remove the slow status caused by miasma and curare, but it will have no effect on the other ailments caused (rotted HP and poison in case of miasma, asphyxiation and poison in the case of curare).
Confusion can be removed with the far more common potion of curing, which lets one save potions of cancellation for more obscure, but no less dangerous, status effects, such as petrification, slow, and Sentinel's Mark. Its ability to cancel Mark makes it particularly useful for Vaults, especially on a character that has had poor luck in finding gear that increases resistance to magic. Finally, if you find yourself with dangerous levels of contamination, one or two of these potions may bring you back to safe levels while avoiding the usual bad effects. However, unless there are many cancellation potions on hand, one should be wary of using cancellation potions simply for the purpose of glow removal outside of combat, as getting hit with an ill-timed Mark or Slow tends to be more dangerous than suffering one or two contamination effects with no monsters around.