Monster frequency
The term monster frequency applies to random monsters generation, as opposed to deliberate polymorph results and more specific ways of monster generation. It refers to a number which can technically range 0–7 (though 6 and 7 are not used in Vanilla NetHack) used internally to determine how frequently a monster is generated; it can be thought of as a relative probability that a particular monster will be selected.
When a monster is randomly being selected, the game picks a random monster subject to the following list of conditions with relative probabilities equal to the ratios of numeric monster frequencies (thus a monster with a 4 is twice as common as a monster with a 2); this can be thought of as generating a list of monsters with each monster appearing a number of times equal to its monster frequency and choosing purely randomly off of this list.
Randomly generated monsters must be:
- No greater in difficulty than the average of the level's difficulty and the player level [1]
- No lower in difficulty than one-sixth that of the current level's difficulty[2]
- Neither unique nor marked as not randomly generated (G_NOGEN) [3]
- Not genocided or extinct
- If you are on the rogue level:
- Represented by an upper case letter
- If you are in Gehennom:
- Not Lawful
- Not marked as not generated in Gehennom (G_NOHELL) (e.g. winter wolf)
- If you are not in Gehennom:
- Not marked as only generated in Gehennom (G_HELL) (e.g. hell hound)
The following terms are used to describe the frequency of a monster in the infobox on monsters' pages:
| Frequency | Description |
|---|---|
| 0 | Not randomly generated |
| 1 | Very rare |
| 2 | Quite rare |
| 3 | Rare |
| 4 | Uncommon |
| 5 | Common |
| 6 | Very common (unused in Vanilla NetHack) |
| 7 | Prolific (unused in Vanilla NetHack) |
Adjustment for aligned levels and branches
The above procedure for generating monsters applies to unaligned levels and branches of the dungeon. If the level or branch has an alignment, then the frequency values of all monsters are adjusted by adding a number depending on the relationship between the monster's alignment and the branch or level's alignment. [4] The numbers that are added to the frequencies can be found in the following table:
| Monster's alignment | Lawful level/branch | Neutral level/branch | Chaotic level/branch |
|---|---|---|---|
| -20 | 0 | 0 | 5 |
| -19 to -17 | 0 | 0 | 4 |
| -16 to -13 | 0 | 1 | 4 |
| -12 | 1 | 2 | 4 |
| -11 to -9 | 1 | 2 | 3 |
| -8 to -5 | 1 | 3 | 3 |
| -4 | 2 | 4 | 3 |
| -3 to -1 | 2 | 4 | 2 |
| 0 | 2 | 5 | 2 |
| 1 to 3 | 2 | 4 | 2 |
| 4 | 3 | 4 | 2 |
| 5 to 8 | 3 | 3 | 1 |
| 9 to 11 | 3 | 2 | 1 |
| 12 | 4 | 2 | 1 |
| 13 to 16 | 4 | 1 | 0 |
| 17 to 19 | 4 | 0 | 0 |
| 20 | 5 | 0 | 0 |
For example, consider the Oracle level, which is neutral. On that level, a kitten, which is neutral (alignment 0) and whose normal frequency is "1", will have its frequency increased to 6. A black unicorn, which is chaotic (alignment -7) and whose normal frequency is also "1", will have its frequency increased to 4.
That does not mean that the kitten is six times more common on the Oracle level than on an unaligned level. Indeed, the numbers are relative frequencies, and since almost every monster has its frequency increased on aligned levels, the kitten will actually be less than six times more common than on an unaligned level.
This explains why some monsters, which have a frequency of "0" but lack the G_NOGEN flag, are not randomly generated on unaligned levels, but can be randomly generated on aligned levels and branches (Gnomish Mines, Oracle, Sokoban, Medusa, Vlad's tower). In Vanilla NetHack, monsters with this property are "baby" monsters (dragons, naga, worms, crocodiles).
SLASH'EM
In SLASH'EM, many monsters that are present in Vanilla NetHack have a higher frequency than they do in Vanilla. The most extreme example are kittens, little dogs and their grown-up forms, all of which have a frequency of "1" in Vanilla and "7" in SLASH'EM. These are the only six SLASH'EM monsters with a "7" frequency. Floating eyes and cockatrices have a "6" frequency. This means that SLASH'EM, unlike Vanilla, uses the entire range of possible frequencies (0–7).
Also, in SLASH'EM, the frequency adjustment for aligned levels and branches is not as large as in Vanilla, as shown in the following table:
| Monster's alignment | Lawful level/branch | Neutral level/branch | Chaotic level/branch |
|---|---|---|---|
| -20 | 0 | 0 | 2 |
| -19 to -11 | 0 | 0 | 1 |
| -10 to -1 | 0 | 1 | 1 |
| 0 | 1 | 2 | 1 |
| 1 to 10 | 1 | 1 | 0 |
| 11 to 19 | 1 | 0 | 0 |
| 20 | 2 | 0 | 0 |
References
This page may need to be updated for the current version of NetHack.
It may contain text specific to NetHack 3.4.3. Information on this page may be out of date.
Editors: After reviewing this page and making necessary edits, please change the {{nethack-343}} tag to the current version's tag or {{noversion}} as appropriate.
