In Nethack, magic cancellation is a property acquired by wearing the right type of armour. It is very useful at all stages of the game, as it reduces your probability of being affected by attacks ranging from poison and lycanthropy to petrification and level drain.

All cloaks and some pieces of body armour provide at least one unit of magic cancellation. Your magic cancellation is the maximum provided by any one piece of armour you are wearing.

When your magic cancellation is at 3, the maximum possible, your chance of being affected by various special attacks is reduced to about 2% of what it would be without any magic cancellation. The following pieces of armour supply maximum magic cancellation: