# Black light

y black light 

Difficulty

7

Attacks

Explode 10d12 hallucination

y black light 

Difficulty

7

Attacks

Explode 10d12 hallucination

Base level

5

Base experience

74

Speed

15

Base AC

0

Base MR

0

Alignment

0 (neutral)

Frequency (by normal means)

2 (Quite rare)

Genocidable

Yes

Weight

0

Nutritional value

0

Size

Small

Resistances

fire, cold, shock, disintegration, sleep, poison, acid, stoning

Resistances conveyed

None

A black light

:

 can fly.

 can flow under doors.

 does not breathe.
 cannot pick up items.
 has no eyes.

 has no limbs.
 has no head.
 is mindless.

 does not have a solid form.

 can see invisible creatures.

 does not eat. (*)
 is neither male nor female.
 is normally generated hostile.

 never leaves a corpse.

 gives out light.

Reference

monst.c#line1047

A black light, y, is a type of monster that appears in NetHack. It is the only other member of the light monster class along with the yellow light. A black light is amorphous, can fly and flow under doors, detect invisible monsters, and possesses every resistance property minus magic resistance.
Like yellow lights, a black light illuminates its surroundings in a 3x3 area centered on itself, but it is always invisible[1] - also like yellow lights, they attack using an explosion directed at the square of their target. This destroys the black light and causes several turns of hallucination if it hits you, while monsters are confused instead if a black light explosion hits them.[2] A black light's explosion will wake nearby sleeping monsters.

Contents

1 Generation
2 Strategy
3 History
4 Variants

4.1 SLASH'EM
4.2 GruntHack
4.3 dNetHack
4.4 xNetHack

5 Encyclopedia entry
6 References

Generation
Black lights are always generated invisible and hostile, and never leave a corpse upon death.
In addition to normal random generation, reading a cursed scroll of light while confused has a 1⁄5 chance of generating a black light unless they are genocided.

The following information pertains to an upcoming version (NetHack 3.7.0). If this version is now released, please verify that it is still accurate, then update the page to incorporate this information.

Reading a cursed scroll of light while confused instead summons 3–4 tame cancelled black lights unless they are genocided.
Strategy
Black lights can be spotted by the illumination they emit in dark areas, especially if the light seems to come from nowhere. They are most easily dealt with by blinding yourself using a blindfold or towel and waiting for it to explode harmlessly at you, then remove the blindfold or towel after. You can also take the brunt of the explosion and apply an immediate cure, such as a unicorn horn - though a potion of full healing can also cure hallucination, this is best saved for more dire scenarios. Wielding Grayswandir if you have the artifact weapon provides hallucination resistance, but does not cure the status and only suppresses its effects.
Try to avoid leaving strong pets near black lights, since they may turn on you in their confusion and batter you to death; this can also happen if you have displacement and the black light targets a displaced image on your pet's square. Monsters have a 1⁄50 chance of recovering from confusion on each of their moves[3] - intelligent pets will cure their confusion using a unicorn horn, making it vital that you equip them with spare ones as soon as possible.
Once you have the see invisible property, you can reliably detect and intercept black lights before they explode; warning can also hint at the presence of a black light as well. As with yellow lights, though it is possible to kill black lights if you can deal with their 0 AC and fast, erratic movement, it is usually quicker to let them explode at you while blinded. Beware of possible black lights anywhere near treasure zoos such as the one in Sokoban and other monster-filled special rooms.

History
The black light first appears in NetHack 3.2.0.

Variants
SLASH'EM
In SLASH'EM, 8-16 black lights are randomly placed across the Lawful Quest at level generation.

GruntHack
In GruntHack, black lights additionally possess magic resistance, further restricting viable ranged options for killing one before it reaches you or a pet.

dNetHack
In dNetHack, four black lights are generated in one of the rooms within the palace of Demogorgon if his level generates as the map of Brine Flats, the third Abyss level.
9⁄20 of randomly-generated monsters in both Nightmare Temple levels of the Chaos Temple Quest will be black lights.

xNetHack
In xNetHack, black light explosions will affect all monsters adjacent to it.

Encyclopedia entry

Strange creatures formed from energy rather than matter, lights are given to self-destructive behavior when battling foes.

 

References

↑ src/makemon.c in NetHack 3.6.7, line 1249

↑ src/mhitm.c in NetHack 3.6.7, line 1207

↑ src/monmove.c in NetHack 3.6.7, line 414