A delayed instadeath is an effect that is not immediately fatal, but will cause you to die instantly after some delay period, regardless of how many hitpoints you have at the time. These effects are generally treatable, so long as you are prepared, and act quickly.
Although the term delayed instadeath sounds self-contradictory, it is the accepted term in the roguelike community. Insta[nt] can be understood as referring only to the final reduction of hitpoints, which occurs in one fell swoop once the delay period is over.
The following delayed instadeaths exist in NetHack:
- Turning to stone as a result of being hit by a cockatrice's special attack, attacked by a monster wielding a cockatrice corpse, or eating a cockatrice egg (and likewise for chickatrices). The standard cure is to eat a lizard corpse. Vegetarians can quaff a potion of acid instead. Acidic corpses are also useful, and other remedies exist.
- Sliming (turning into green slime). Curable by setting yourself on fire or casting Cure Sickness.
- Food poisoning from eating an old corpse or disease from the sickness attack of Juiblex, Scorpius, Demogorgon or Pestilence, or as one of the effects of applying a cursed unicorn horn. Curable by applying a non-cursed unicorn horn (risky, as it may fail) or casting Cure Sickness.
- Sinking in lava. Fix this by praying, zapping a wand of cold downwards or teleporting.
- Strangulation, from wearing an amulet of strangulation. Instantly curable by removing the amulet, but amulets of strangulation are normally generated cursed.
- Eels, krakens, and couatls can cause delayed drowning.
- Purple worms and trappers can digest the player, a delayed instadeath if the monster is not killed. The exact time of death is random and based on attributes.
Normally, Prayer will not save you from the last two delayed instadeaths, though a sufficently angry god could unintentionally save you from digestion by blasting the monster with lightning while trying to kill you.