# Monster difficulty
A monster's difficulty is a number from 1 to 57 which represents the game's idea of how tough a monster is. It loosely correlates with a monster's base level, but is often higher for monsters with special properties that might make them tougher.
Difficulty is primarily used in the normal mechanism of monster generation to decide whether a candidate monster is appropriately difficult for the player to encounter. A monster is "too strong" to be randomly generated when its difficulty is greater than the average of your experience level and your dungeon level. It is "too weak" to be randomly generated when its difficulty is less than your dungeon level divided by 6, rounded down. (For this purpose, once you have the Amulet of Yendor your dungeon level is considered to be that of the Sanctum, and in the endgame to be the depth of the Sanctum plus half your experience level.) Most of the less common mechanisms of monster generation do not have similar limits.
Other effects of difficulty include:

How much your god appreciates a sacrificed corpse (the dead monster's experience level doesn't matter).
Whether your god will be mollified, if they are angry. You must sacrifice a monster corpse of difficulty 7 or greater (11 or greater if you are chaotic) in order to mollify the god.
The type of offensive, defensive, or miscellaneous item a monster may receive.
Whether a monster considers itself weak enough to try polymorphing itself.
Contents

1 Difficulty values
2 Difficulty algorithm (3.6.1 and earlier)
3 References

Difficulty values
This is a list of monsters sorted by difficulty, then by experience value.
This table was generated with the use of a modified version of makedefs to calculate experience values as well, and is believed by the author to be accurate.  If there are discrepancies between these and those listed in the articles, please correct the article.

Name

Experience

Difficulty

Demogorgon
3297
57

Asmodeus
3225
53

Baalzebub
2333
45

Dispater
1923
40

Geryon
1625
36

Orcus
1445
36

Pestilence
1431
34

Famine
1431
34

Death
1431
34

Wizard of Yendor
1411
34

Vlad the Impaler
1087
32

Master Kaen
1095
31

Yeenoghu
1073
31

high priest
1054
30

Grand Master
1053
30

Arch Priest
876
30

arch-lich
915
29

Juiblex
899
26

Archon
730
26

mail daemon
1
26

Medusa
634
25

Master of Thieves
588
24

Cyclops
662
23

Neferet the Green
593
23

Norn
588
23

Lord Sato
588
23

King Arthur
588
23

Chromatic Dragon
586
23

Nalzok
585
23

Minion of Huhetotl
585
23

kraken
1574
22

Croesus
746
22

mastodon
611
22

Shaman Karnov
583
22

Pelias
583
22

Orion
583
22

Lord Carnarvon
583
22

Hippocrates
583
22

Twoflower
581
22

Thoth Amon
547
22

Ixoth
545
22

iron golem
545
22

ki-rin
552
21

master lich
494
21

balrog
575
20

titan
553
20

yellow dragon
535
20

white dragon
535
20

silver dragon
535
20

red dragon
535
20

orange dragon
535
20

green dragon
535
20

gray dragon
535
20

blue dragon
535
20

black dragon
535
20

Master Assassin
503
20

Dark One
498
20

storm giant
536
19

Ashikaga Takauji
488
19

Lord Surtur
486
19

Angel
485
19

master mind flayer
416
19

jabberwock
489
18

glass golem
409
18

demilich
376
18

minotaur
504
17

Scorpius
474
17

purple worm
474
17

Nazgul
376
17

pit fiend
422
16

Olog-hai
325
16

guardian naga
295
16

stone golem
345
15

nalfeshnee
341
15

baluchitherium
331
15

sandestin
308
15

aligned priest
294
15

shopkeeper
287
15

vampire lord
399
14

skeleton
359
14

shade
357
14

ice devil
351
14

disenchanter
301
14

hell hound
290
14

guard
284
14

captain
277
14

prisoner
272
14

trapper
270
14

lich
269
14

frost giant
296
13

ettin
291
13

Oracle
286
13

bone devil
285
13

baby yellow dragon
272
13

baby white dragon
272
13

baby silver dragon
272
13

baby red dragon
272
13

baby orange dragon
272
13

baby green dragon
272
13

baby gray dragon
272
13

baby blue dragon
272
13

baby black dragon
272
13

titanothere
267
13

mind flayer
263
13

water troll
246
13

nurse
245
13

golden naga
239
13

vampire
327
12

Aleax
298
12

hezrou
267
12

clay golem
249
12

ghost
238
12

queen bee
225
12

watch captain
221
12

valkyrie
221
12

tourist
221
12

samurai
221
12

rogue
221
12

lieutenant
221
12

knight
221
12

black pudding
221
12

barbarian
221
12

archeologist
221
12

wizard
216
12

ranger
216
12

priestess
216
12

priest
216
12

healer
216
12

elf
216
12

cavewoman
216
12

caveman
216
12

lurker above
214
12

ice troll
205
12

rock troll
198
12

umber hulk
194
12

salamander
159
12

fire giant
254
11

monk
211
11

winged gargoyle
207
11

water demon
196
11

Elvenking
196
11

ogre king
194
11

doppelganger
191
11

zruty
186
11

giant mimic
186
11

couatl
180
11

marilith
177
11

vrock
176
11

xorn
139
11

elf-lord
123
11

electric eel
1129
10

flesh golem
186
10

barbed devil
179
10

hill giant
174
10

erinys
158
10

fire vortex
142
10

fire elemental
134
10

black naga
132
10

water elemental
126
10

earth elemental
126
10

air elemental
126
10

sergeant
118
10

giant mummy
116
10

cobra
90
10

long worm
169
10

horned devil
147
9

xan
120
9

wumpus
118
9

stalker
113
9

large mimic
113
9

giant zombie
113
9

baby purple worm
113
9

baby long worm
113
9

steam vortex
112
9

glass piercer
106
9

shark
104
9

winter wolf
102
9

hell hound pup
102
9

energy vortex
101
9

warhorse
97
9

troll
97
9

ogre lord
97
9

sasquatch
95
9

pit viper
93
9

quantum mechanic
92
9

mountain centaur
88
9

green slime
164
8

cockatrice
149
8

stone giant
127
8

giant
127
8

succubus
122
8

incubus
122
8

wraith
120
8

djinni
97
8

gargoyle
95
8

wood golem
92
8

warg
92
8

small mimic
92
8

ettin mummy
92
8

shocking sphere
91
8

freezing sphere
91
8

flaming sphere
91
8

ochre jelly
88
8

dwarf king
83
8

red naga
82
8

python
82
8

pyrolisk
82
8

watchman
78
8

soldier
78
8

Grey-elf
78
8

leocrotta
76
8

gelatinous cube
76
8

carnivorous ape
76
8

tiger
73
8

guide
71
8

apprentice
71
8

acolyte
71
8

rust monster
70
8

scorpion
67
8

abbot
66
8

forest centaur
64
8

gremlin
61
8

giant eel
1075
7

chickatrice
136
7

owlbear
94
7

barrow wight
90
7

tengu
76
7

large dog
76
7

large cat
76
7

ice vortex
74
7

black light
74
7

leather golem
73
7

human mummy
73
7

ettin zombie
73
7

elf mummy
73
7

crocodile
73
7

chameleon
73
7

mumak
68
7

warrior
66
7

vampire bat
66
7

thug
66
7

roshi
66
7

page
66
7

orc-captain
66
7

ninja
66
7

winter wolf cub
64
7

giant spider
64
7

student
61
7

ogre
61
7

neanderthal
61
7

hunter
61
7

horse
61
7

Green-elf
61
7

chieftain
61
7

attendant
61
7

yeti
59
7

panther
59
7

lynx
59
7

werewolf
56
7

water moccasin
48
7

quasit
36
7

iron piercer
63
6

werewolf
61
6

spotted jelly
61
6

gnome king
61
6

quivering blob
59
6

wolf
56
6

piranha
56
6

orc mummy
56
6

lizard
56
6

gold golem
56
6

giant beetle
56
6

dwarf mummy
56
6

brown pudding
56
6

dust vortex
54
6

white unicorn
51
6

gray unicorn
51
6

dwarf lord
51
6

black unicorn
51
6

plains centaur
49
6

snake
48
6

Woodland-elf
46
6

raven
46
6

Kop Kaptain
46
6

rope golem
44
6

jaguar
44
6

ape
41
6

soldier ant
37
6

fire ant
34
6

blue jelly
45
5

yellow light
44
5

housecat
44
5

dog
44
5

dingo
44
5

human zombie
41
5

gnome mummy
41
5

orc shaman
38
5

gnomish wizard
38
5

violet fungus
34
5

jellyfish
34
5

Uruk-hai
33
5

Mordor orc
33
5

Kop Lieutenant
33
5

bugbear
33
5

killer bee
31
5

wood nymph
28
5

water nymph
28
5

mountain nymph
28
5

lemure
28
5

ghoul
28
5

leprechaun
59
4

fog cloud
38
4

woodchuck
35
4

rock mole
35
4

imp
33
4

gnome lord
33
4

pony
31
4

straw golem
28
4

rock piercer
28
4

red naga hatchling
28
4

paper golem
28
4

kobold mummy
28
4

guardian naga hatchling
28
4

gray ooze
28
4

golden naga hatchling
28
4

elf zombie
28
4

black naga hatchling
28
4

baby crocodile
28
4

kobold shaman
27
4

Kop Sergeant
22
4

hill orc
22
4

dwarf
22
4

giant ant
20
4

centipede
19
4

wererat
17
4

werejackal
17
4

rothe
17
4

rabid rat
17
4

monkey
17
4

wererat
22
3

werejackal
22
3

kobold lord
22
3

giant bat
22
3

little dog
20
3

kitten
20
3

homunculus
19
3

orc zombie
17
3

iguana
17
3

floating eye
17
3

dwarf zombie
17
3

orc
13
3

Keystone Kop
13
3

hobgoblin
13
3

gnome
13
3

manes
8
3

garter snake
8
3

cave spider
8
3

shrieker
28
2

large kobold
13
2

hobbit
13
2

gas spore
12
2

red mold
9
2

green mold
9
2

brown mold
9
2

acid blob
9
2

yellow mold
8
2

gnome zombie
8
2

giant rat
8
2

gecko
8
2

coyote
8
2

human
6
2

bat
6
2

kobold
6
1

goblin
6
1

lichen
4
1

fox
4
1

sewer rat
1
1

newt
1
1

kobold zombie
1
1

jackal
1
1

grid bug
1
1

Difficulty algorithm (3.6.1 and earlier)
In versions of NetHack prior to 3.6.2 (and derived variants), the monster's difficulty was calculated during compilation using the below algorithm, and stored in monstr.c. As of NetHack 3.6.2, difficulty is now stored in the monst.c as part of the mons array. All monsters have the same difficulty in 3.6.1 and 3.6.2.
Start by setting the difficulty to the monster's base level, as defined directly in monst.c.[1]
If the monster's base level is greater than 49 (meaning that it's either a mail daemon or a demon lord), instead set the initial difficulty to (base level - 6) / 2.
Next, compute a bonus based on properties of this monster:

Start at 0.
Add 1 if the monster generates in small groups.
Add 2 if the monster generates in large groups.
Add 1 if the monster is capable of ranged attacks: whether it has any weapon, spellcasting, gaze, spit, or breath attacks.
Add 1 if the monster's base AC is between 0 and 3, inclusive.
Otherwise add 2 if the monster's base AC is -1 or lower.
Add 1 if the monster's speed is 18 or higher.
For each attack the monster has, add together all the following bonuses:
Add 1 if the attack is non-passive.
Add 1 if the attack is arcane spellcasting (AT_MAGC).
Add 1 if the monster is strong and the attack is a weapon attack (AT_WEAP).
Add 2 if the attack has a damage type of AD_DRLI (drain life), AD_STON (stoning), AD_DRST (strength poison), AD_DRDX (dexterity poison), AD_DRCO (consitution poison), or AD_WERE (lycanthropy).
Add 1 if the damage type is none of the above six types and is also not AD_PHYS (physical damage), and the monster is not a grid bug.
Add 1 if the maximum attack damage for this attack is 24 or higher.
Subtract 2 if the monster is a leprechaun.[2]
Then, modify difficulty based on what the bonus worked out to be:

If the total bonus equals 0, subtract 1 from difficulty.
If the total bonus is 6 or higher, add half of the bonus, rounded down, to difficulty.
Otherwise, if the total bonus is between 1 and 5, add 1 + one-third of the bonus, rounded down, to difficulty.
Finally, if difficulty is negative (only possible with very weak monsters like lichens), set it to 0.

References

↑ util/makedefs.c in NetHack 3.6.0, line 2117

↑ util/makedefs.c in NetHack 3.6.0, line 2156: This is evidently to compensate for leprechauns' base level being artificially inflated, and to cancel out the 2 points they get from their gold-stealing attack. It is unclear why the bonus is not simply set to 0 here.

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