Monster detection
Monster detection is a property in NetHack that allows a hero to see all monsters on the current dungeon level.
Monster detection can be obtained by the hero from either quaffing the potion of monster detection, quaffing from a fountain, or casting the detect monsters spell. Monsters will not use any of these methods.
Description
Monster detection can occur in multiple forms, depending on the source of the property:[1]
- Quaffing a non-blessed potion of monster detection, quaffing from a non-magical fountain with a 1⁄30 chance or casting the spell of detect monsters cast at Basic or lower skill will reveal the current location of all monsters that on the dungeon level.[2][3] This will display the monsters and their locations against a blank map similar to a potion of object detection:[4][5] the hero can navigate this screen by moving their cursor to highlight particular monsters, and any other key that does not perform a navigation action will exit this screen. Monster locations are not recorded when returning to normal play.
- Quaffing a blessed potion of monster detection, or casting the spell of detect monsters cast at Skilled or higher, will grant monster detection as an intrinsic property and continuously display the position of all monsters on the current level for several turns.[6][7] This form of the property is sometimes informally referred to as "blessed monster detection" or "passive monster detection" and lasts for 21–60 turns per usage of the Skilled (or better) spell or the blessed potion, and additional uses will only add 1 more turn to the duration if the hero already has at least 300 turns of passive monster detection.[8][9]
- In wizard mode, the #wizintrinsic extended command can be used to grant 30 (more) turns of monster detection as from the blessed potion or the Skilled (or better) spell. The property's current duration can be seen via the #timeout extended command.
The hero exercises wisdom when quaffing the potion or casting the spell, and the locations of invisible monsters are always revealed even if the hero cannot see invisible normally.[10] Using the spell or potion while hallucinating will have the same effects as described above, but will print different messages and display monsters as their hallucinated identities.
Monsters seen via the latter forms of monster detection are valid targets for the fireball and cone of cold spells cast at Skilled or higher in attack spells. A large box containing Schroedinger's Cat cannot have its contents revealed indirectly by monster detection.
The following information pertains to an upcoming version (3.7.0). If this version is now released, please verify that the information below is still accurate, then update the page to incorporate it.
Per commit 2e43f83d, enlightenment in wizard mode also reveals the number of turns remaining for monster detection.
Per commit bf53ff9d, quaffing from a fountain gives proper feedback if the potion effect occurs while the hero is the only 'monster' on the level.
Per commit dfac5fbf, quaffing a blessed potion grants passive monster detection for 100-199 more turns if the hero does not have at least 300 turns of the property already.History
The monster detection property first appears with the potion of monster detection in Hack for PDP-11, which is based on Jay Fenlason's Hack. The property also appears in Hack 1.0 and every version of the game since then.
From Hack 1.0 to NetHack 3.4.3, including some variants based on those versions, a hero that attacks a hiding monster which they can see via blessed monster detection will "reveal" that monster instead of immediately attacking normally—this is bug #C343-197, and is fixed in June 2006 via commit c3745836. Additionally, pets will be displayed improperly via blessed monster detection if the hilite_pet option is set—this is bug bug NM343-6, and is fixed for NetHack 3.6.0 in June 2015 via commit 86b84568 and commit f86bbca9.
Messages
- You sense the presence of monsters.
- You quaffed a non-blessed potion of monster detection, or cast the detect monsters spell at Basic or lower.
- You <are/were> sensing the presence of monsters.
- You have intrinsic monster detection, as seen via enlightenment or the end-of-game screen.
- You feel threatened.
- You quaffed a non-blessed potion of monster detection or cast the detect monsters spell at Basic or lower, but there were no monsters on the current level, and you are not a beginner.
- You get the heebie jeebies.
- As above, while hallucinating.
- You feel lonely.
- You quaffed a blessed potion of monster detection detect monsters spell at Skilled or higher, and there are no monsters currently on the level at that time.
The following information pertains to an upcoming version (NetHack 3.7.0). If this version is now released, please verify that the information below is still accurate, then update the page to incorporate it.
The following message is added per commit bf53ff9d above.
- The water tastes like nothing.
- You quaffed from a fountain and got the detect monsters effect, but you are the only monster on the level.
Variants
Variants of NetHack generally add more items that grant monster detection, often including artifact effects.
GruntHack
In GruntHack, monster detection can partially "see through" the effects of a monster's displacement: the screen will display their actual location alongside their displaced image, making it possible for their glyph to show up on two different squares.
dNetHack
In dNetHack, notdNetHack, and notnotdNetHack, some monsters have a form of vision that behaves as an innate type of monster detection.
Various artifacts can grant monster detection in some form:
- Nenya is an unaligned, intelligent and elf-favoring diamond ring that can be put on to gain blessed monster detection.
- The Crown of the Percipient is a neutral, intelligent artifact helm of brilliance made of flesh that is the crowning gift for Drow Healers and other heroes that worship Pen'a, and grants blessed monster detection while worn.
- The All-seeing Eye of the Fly is a lawful, large-sized and intelligent helm of telepathy that Baalzebub is always generated with. A hero wearing the artifact gains blessed monster detection, and using far look on monsters seen via the property from the artifact will show their DR breakdown as well as their current inventory.
NetHack Fourk
In NetHack Fourk, sylph heroes gain intrinsic blessed monster detection at experience level 16.
FIQHack
In FIQHack, a monster with displacement that is seen via monster detection will not have a displaced image visible, unlike in GruntHack.
SlashTHEM
In SlashTHEM, zapping a wand of wonder has a 1⁄21 chance of granting blessed monster detection for 11-30 (more) turns and exercising wisdom—if the hero already has at least 300 turns of blessed monster detection, this effect will only add 10 more turns.
References
- ↑ src/potion.c in NetHack 3.6.7, line 816: both potion and spell use the same code
- ↑ src/potion.c in NetHack 3.6.7, line 845: calls monster_detect() in detect.c
- ↑ src/detect.c in NetHack 3.6.7, line 783: monster_detect() function
- ↑ src/detect.c in NetHack 3.6.7, line 807: temporary map is drawn using this code
- ↑ src/detect.c in NetHack 3.6.7, line 837: temporary map navigation
- ↑ src/potion.c in NetHack 3.6.7, line 818
- ↑ src/detect.c in NetHack 3.6.7, line 834
- ↑ src/potion.c in NetHack 3.6.7, line 817: both the spell and potion use the same code
- ↑ src/potion.c in NetHack 3.6.7, line 825
- ↑ src/potion.c in NetHack 3.6.7, line 847
