Dungeon fern

The dungeon fern is a subset of monsters that appear in multiple variants of NetHack. Dungeon ferns and their relatives can be found in UnNetHack, dNetHack, notdNetHack, notnotdNetHack, and Hack'EM—their specific abilities, functions and classification depend on the variant where they appear.

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Common traits

Dungeon ferns are stationary with a low speed of 2, and have no directly-damaging attacks. However, if a hero is within roughly ten squares of a fern, they have a chance each turn of using a spore-making attack (or simply a spore attack) that is coded as a gaze attack: this attack has a ¹⁄₂ chance of creating fern spores during each of their turns. The main differences among the four species of dungeon fern are the types of damage caused by their exploding spores, and the terrain in which they can reproduce.

Fern spores are spherical creatures across all variants, and are more dangerous relatives of gas spores with poison resistance. These fern spores will attack the hero and grudge other monsters in the dungeon, and most other monsters will mutually grudge them in return—this is because ferns reproduce themselves by generating the spores, which in turn will attempt to explode and "seed" themselves in the terrain. A dungeon fern's spores have two means of attacking: an active explosion attack that releases a small plume of poison clouds, and an on-death explosion that hits monsters in a 3x3 square centered on its location, similar to the gas spore.

Spore explosions have a ¹⁄₃ chance of creating another dungeon fern, with a ¹⁄₆ chance of creating a full-grown fern of the same type as the spore and otherwise creating a sprout of that dungeon fern: fern sprouts are stationary and can create spores like fully-grown ferns, but act at the same low speed of 2 and have a lower chance of ¹⁄₄ to create spores so each turn.

UnNetHack

In UnNetHack, ferns are part of the fungus or mold monster class, F, which is renamed to "fungus, mold, or fern" for the far look and what is commands. Monsters in the dungeon that are not fern monsters or Devil's Snare share a mutual grudge with fern spores.

UnNetHack features the following dungeon fern monsters:

• F dungeon fern
  • F dungeon fern sprout
  • e dungeon fern spore
• F arctic fern
  • F arctic fern sprout
  • e arctic fern spore
• F blazing fern
  • F blazing fern sprout
  • e blazing fern spore
• F swamp fern
  • F swamp fern sprout
  • e swamp fern spore
• e fern spore

Dungeon ferns and swamp ferns (and their sprouts) produce spores that deal physical damage with their explosion attack, while blazing ferns and their sprouts produce spores that deal fire damage with their explosion attack, and arctic ferns and their sprouts produce spores that deal cold damage with their explosion attack. Blazing ferns, sprouts and spores possess fire resistance, while arctic ferns, sprouts and spores possess cold resistance, and all spores possess poison resistance.

Fern reproduction is limited to the following terrain for each monster type:

• Dungeon ferns can reproduce themselves using normal floor squares and muddy swamp.
• Arctic ferns can reproduce themselves using pools, moats, ice squares, and muddy swamp.
• Blazing ferns can reproduce themselves using lava squares.
• Swamp ferns can reproduce themselves using muddy swamp.

Reading a blessed scroll of stinking cloud while confused will generate up to three generic fern spore monsters (e), which are not randomly generated otherwise—they can produce any of the four species of ferns, depending on if they explode over appropriate terrain.

dNetHack

In dNetHack, notdNetHack and notnotdNetHack, dungeon ferns and sprouts are part of the plant monster class, which uses the { glyph.

dNetHack features the following dungeon fern monsters:

• { dungeon fern
  • { dungeon fern sprout
  • e dungeon fern spore
• { swamp fern
  • { swamp fern sprout
  • e swamp fern spore
• { burning fern
  • { burning fern sprout
  • e burning fern spore

Hack'EM

Hack'EM adds the dungeon ferns from UnNetHack, placing the ferns and sprouts within the fungus or mold monster class as UnNetHack does:

• F dungeon fern
  • F dungeon fern sprout
  • e dungeon fern spore
• F arctic fern
  • F arctic fern sprout
  • e arctic fern spore
• F blazing fern
  • F blazing fern sprout
  • e blazing fern spore
• F swamp fern
  • F swamp fern sprout
  • e swamp fern spore
• e fern spore

Strategy

In general, it is important to destroy dungeon ferns quickly unless you possess the means to contain out-of-control growth—the dangerous effects of the spores' poison clouds can be mitigated by poison resistance or unbreathing, and if you lack either of these properties, standing at a diagonal to the spore when it bursts will give you a significant chance of being outside of the cloud when it forms. A careful player can take advantage of this and lure spores toward otherwise difficult monsters without poison resistance or unbreathing.

Origin

Ferns are a group of real plants with characteristic leaves. They are primitive, having neither seeds nor flowers; they reproduce with spores, hence the spore attack in the game.

Encyclopedia entry

These dreadful weeds have been driven to extinction on the
surface, yet deep within the dark and damp of the dungeon
they still flourish. When it detects the motion of nearby
creatures, the dungeon fern releases a deadly, poisonous
spore, which quickly detonates to propagate the species.

Residents of the dungeon have learned how not to disturb
the dungeon fern, and will attack its spores on sight to
keep them from overtaking their home.