Vibrating square

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Vibrating square level
Location Level 19-23 of
Gehennom
Bones No
Mappable Yes
Teleportable Yes
Diggable floor No
Diggable walls Yes

The vibrating square is the square where the invocation ritual is to be performed for entry into Moloch's Sanctum. It is always located on the penultimate dungeon level of Gehennom, which could be between levels 44 and 52. It is the lowest level that can be reached without performing the ritual; until the ritual is performed, there is no staircase leading down from that level. Only the Sanctum level has a higher dungeon level number.

The level with the vibrating square is in most other respects an ordinary maze level of Gehennom.

Identification[edit]

The only way to locate the vibrating square is to move over it, at which point you will get the message: "You feel a strange vibration under your <feet>.", or "You feel a strange vibration beneath you" if you are flying or levitating. This message will always occur if you walk on top of the vibrating square, but not if you jump over it or are carried over it by an engulfing monster. There are no other special features of the square.

The vibrating square cannot appear near the edge of the screen nor the staircase, because there must always be room for the ring of fire traps and moats to appear around it.[1] Specifically, it will be at least five squares from the left and right sides of the map, at least four squares from the top or bottom, and not within a 23x23 square area centered on the upstair. It will also not be in a straight line with the upstair or on the same square as a trap, although it may be on the same square as a boulder or other item. It helps to mark ineligible places (and where you have searched) on a screen shot. Some players polymorph into a xorn so they can traverse the level line by line, or into an air elemental to reduce the number of turns spent searching.

Although the vibrating square cannot be placed on a trap, traps can be created on its location (except in NetHack 4), meaning that a drum of earthquake does not help to find it. (If a pit is created on the vibrating square, you can remain trapped in it even after performing the invocation; this is bug C343-192.)

Many players will mark the vibrating square by leaving an object on it once they have located it. This is one of the leading uses for the mostly useless iron chain, but it is hardly necessary to find one for this purpose. Any object that most monsters will not want to pick up, or is protected by an engraved "Elbereth," will suffice, and the vibrating square itself never changes location. (Marking it with the Candelabrum of Invocation or Bell of Opening is also a viable option; you won't need them again until you return to the position, saving weight in the meantime.) The general location of the square can also be permanently marked with a via lighting it (using the scroll, wand, or spell, or digging out the surrounding walls (so that it can be located via magic mapping even in case of amnesia; if you dig a path between it and the stairs, you won't even need mapping, and it will help speed up the ascension run). It is actually strictly better to not use a turn and record its location in some other way (such as #nameing an item with its co-ordinates), but in most games, the turn saved by this is irrelevant compared to the convenience. In NetHack 4, the square, once identified, is automatically marked with a (^), and has a red background if the bgbranding option is set.

This MSGTYPE setting makes it harder to accidentally miss the vibrating square if you are using the tty interface:

MSGTYPE=stop "You feel a strange vibration under your *."
MSGTYPE=stop "You feel a strange vibration beneath you."

In this example map, the eligible places are marked with (X). Red spots are too close to the edge, blue ones in line with the stairs, and yellow ones too close to the upstairs. You can mouse over the map to see what is wrong with some of the squares.

 ----------------------------------------------------------------------------- 
 |.......|...............|.......................|.|...|.......|.........|...| 
 |.-----.|.-----------.---.-----.-----.---.-----.|.|.|.|.|.---.|.|.-----.---.| 
 |.|.....|...|.......|.....|...|...|...|.|.|...|...|.|...|.|.|.|.|...|.|...|.| 
 |.---X---X---X-----X---X---X|X-----X--|.|.|.|.|--.|.----|.|X|X|X|--X|X---.|.| 
 |...|X|XXX|XXX|X|X|XXX|X|XXX|XXXXXXX|.|...|.|.|...|...|.|.|XXX|X|X|X|XXX....| 
 |.|.---X---X---X|X---X|X|X-----------.|.---.|.-------.|.|.|----X|X|X-------.| 
 |.|.....|...|...|...|.|.|.|.......|.....|...|..<|.....|.|.|.....|.|.......|.| 
 |-------|X---X---X--|X--|X|X-----X|X-----.-----.|.-----.|.|X-----X|------.--| 
 |...|XXX|X|XXX|XXXXX|XXX|XXXXXXX|X|X|.....|.|...|.......|..X|XXXXX|X|XXX|...| 
 |.|.|X|X|X|X-------X---X|------X|X|--.-----.|.---------.-----X---X|X|X|X---.| 
 |.|..X|XXX|X|XXXXX|XXX|X|XXXXX|X|X|X..|.....|.............|XXXXX|XXX|X|X....| 
 |.|------X|X---X|X|X|X|X|X---X|X|X|X|.|.---.-------------.-----X|--X|X|----.| 
 |.|..XXXXX|XXX|X|XXX|X|XXX|X|X|X|XXX|...|.....|.......|.|..XXXXX|XXX|X|X..|.| 
 |.-----------X|X|----X-----X|X|----X|--------.|.-----.|.|.-----X|----X|X|.|.| 
 |...|.......|.|.|.......|...|.|...|.|.....|...|...|...|...|...|.|.....|.|.|.| 
 |.|.|.---.---.|.---------.|.|.|.|.---.---.-------.|.-------.|.---.-----.---.| 
 |.|.....|.....|...........|.....|.....|...........|.........|.....|.........| 
 ----------------------------------------------------------------------------- 

SLASH'EM[edit]

In SLASH'EM, the level with the vibrating square can have various types of borders instead of walls: clouds, lava, water, ice, or, worst of all, nearly indestructible iron bars. If you get any type of borders other than walls or iron bars, it is generally easier to scan the whole level line-by-line while levitating for the vibrating square. Note that this is not quicker in game turns, since you are walking over more squares, and a careful speedrunner will still want to scan for the vibrating square normally.

In the case of clouds and ice, however, this will not work. The vibrating square can be placed on one ice and cloud squares, presumably since they can be walked over, and the whole eligible region of the level must be searched, not just the "path." Notably, if the vibrating square is made of ice, this can be melted as usual, leaving the square underwater.

UnNetHack[edit]

UnNetHack has the player start feeling vibrations when they step within two tiles of the square, regardless of intervening walls, making the search process much easier.

References[edit]

  1. mkmaze.c, line 587