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The piercer, p, is a monster class in NetHack that contains the following monsters:

  • p rock piercer
  • p iron piercer
  • p glass piercer

Common traits

Piercers are carnivorous animals that are always generated as hostile. They are capable of hiding on the ceiling, and attempt to fall onto you just as you pass beneath. The fall itself deals 4d6 damage regardless of piercer type, but is rather inaccurate and dependent on your AC - it has only a 35 chance of hitting you at 10 AC, and will always miss a player with at least −2 AC. Wearing any metallic helm will reduce the attack's damage to 2 HP, with the blow glancing off it.[1] Explicitly revealing a piercer via methods such as searching or telepathy will prevent the falling attack from occurring.

Outside of this, piercers are the slowest non-sessile monsters in the dungeon with a measly 1 speed - their sole bite attack is somewhat damaging for the point at which you first encounter them, but this can easily be mitigated by keeping your distance. Piercers have relatively low AC that can pose a problem to players lacking a decent weapon, but are otherwise trivial to dispatch.

All piercers leave ordinary fleshy corpses. They are safe to eat, and provide a decent amount of nutrition.


Rock piercers are generally the first type of piercer you will encounter, and have a weaker AC of 3. It also gives less nutrition compared to the other piercers.


A rock piercer will always appear on the Plane of Earth.

Glass piercers are acid resistant, and are the only piercers to possess any kind of resistance.


The piercer has been present in the game since Jay Fenlason's Hack - NetHack 3.0.0 introduces the three distinct types of piercer.


A piercer is a snail-like gastropod that first appeared in Dungeons & Dragons. It has a shell that resembles a stalactite, and clings to the ceiling of caverns and dungeons, mimicking a stalactite and falling down to impale anything that passes underneath. The "bestiary of Xygag" mentioned in the encyclopedia entry is an in-universe equivalent to the Dungeons & Dragons Monster Manual - the excerpt originates in "The Ecology of the Piercer" by Chris Elliott and Richard Edward, published in issue #72 of Dragon magazine.


A <foo> piercer suddenly drops off the ceiling!
A hostile piercer attempted to land on you.
You are almost hit by a falling <foo> piercer!
The piercer's falling attack missed.
You are hit by a falling <foo> piercer!
The piercer hit you and inflicted damage.
Its blow glances off your helm.
As above, but you are wearing a metallic helm, reducing the damage to 2.


Lethe patch

In the Lethe Gorge within the original Lethe patch, the second level contains an iron piercer along with another random p.

Convict patch

In the Convict patch as well as variants that incorporate the role, the lower filler levels on the Convict quest contain an assortment of piercers.


In xNetHack, piercers have a dexterity-based percentage chance of missing the player, and a speed-dependent chance of missing a targeted monster. A metallic helm will only halve the damage dealt from being hit by a falling piercer.


dNetHack adds the heaven piercer, which is much faster and stronger than most piercers - although still relatively slow - and can stun the player with its bite.

The Elder Sign is a ward that can repel piercers, as is the hallucinatory Cerulean Sign.

Encyclopedia entry

Ye Piercer doth look like unto a stalactyte, and hangeth
 from the roofs of caves and caverns. Unto the height of a
 man, and thicker than a man's thigh do they grow, and in
 groups do they hang. If a creature doth pass beneath them,
 they will by its heat and noise perceive it, and fall upon
 it to kill and devour it, though in any other way they move
 but exceeding slow.

the Bestiary of Xygag