A hole is a trap, but it is always visible. It shows as ^ or on the screen. A hole causes you, affected monsters, and objects to fall through at least to the next level. A trapdoor is very similar to a hole.
If you step on a hole, there is a chance you escape its effects. This chance is normally 20%, but 0% if fumbling or in Sokoban, and 100% if outside Sokoban and levitating, flying, being held, polymorphed into a huge monster etc. In case you are affected, you will fall down at least one dungeon level: 75% chance of 1, 19% of 2, 5% of 3, 3*4^(-n) of n levels down. However, you always stay in your current branch (except when falling from the Castle into the Valley of the Dead). All eligible tiles of your destination level are equally likely. Your destination level and tile are re-selected independently each time you fall through the trap. Adjacent or leashed pets and follower species will come along, and each object only on your own tile has a 33% chance of following (3% for boulders). They will be placed on your landing spot or adjacent to it.
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"If a monster steps on a hole, chance of escaping (especially if known trap type, or player-known trap for pets), deliberate usage as an escape route if damage. Monsters and unattended objects will always move down one level.
Autopickup takes effect both on top of the hole and on your destination square.
Objects: thrown or kicked onto hole, or "agitated" if a freshly-dug hole or a pet on a cursed leash kept you from falling through. The only case they don't fall through is if you escaped the trapdoor and the game doesn't even show the trap symbol.
You can fall past hard floor levels. Reference Dogley Dimension."
If you or a monster (see below) step on to a hole and fail to escape it, or an item is thrown onto the same square as a hole, it will fall a random number of dungeon levels, with increasingly less chance of higher numbers of levels. A pet that is leashed to you may be dragged after you, with a chance that the leash may break and the pet remains on the level with the hole.
The falling object will always remain in the same dungeon branch as the hole. Note that this random calculation is redone every time the hole is fallen through - even if the same hole is used on the very next action (even if it is the same turn due to having intrinsic or extrinsic speed), the dungeon level calculated may be different.
Once the random number of levels has been calculated, the falling object is placed randomly on the level and any objects that fell in as part of the same turn are placed nearby. Normal room-and-corridor levels will always place falling objects in a valid room.
Some dungeon levels are made of hard material of which the floor is undiggable, with a message to that effect. Some of these levels will, however, let you create a pit (see below) but not a hole.
Holes in Sokoban, only possible on levels 2, 3 or 4, are special. These holes have air currents that will pull you into them even if you are flying, jumping or levitating over them. The only way to circumvent a hole in Sokoban without filling it with a boulder is to throw an heavy iron ball (chained to you) over the hole. This carries a Luck penalty.
Fast creation of holes
Slow creation of holes
You can dig downward with a pick-axe or dwarvish mattock to make a hole, but this process is very slow and not useful for escaping monsters. The first time you dig downward you create a pit - as you are digging it, you do not fall in, which matters for those with cockatrice corpses in their posession. Beware, however, that items on the adjacent squares may fall in the pit.
If the level allows you to and you again dig downwards, the pit becomes a hole and any items on the square will fall through to the same random level as you.
Sometimes a monster will intentionally jump into an existing hole to escape. If a monster has a wand of digging, it might zap it downward as well to create a hole, especially if it is damaged. This can be annoying; whenever you find that dwarf (for example), it makes another hole, and when you finally kill it, the wand can be empty. Monsters with digging tools will not create pits or dig downwards if in a pit to escape.
Creatures of size "huge" or larger will not fit into holes or pits and can walk across them. Flying creatures can also traverse holes.
- Most common execution sequence: allmain.c, line 408, cmd.c, line 1940, hack.c, line 1406, hack.c, line 1526, trap.c, line 944
- trap.c in NetHack 3.4.3, line 619
- trap.c in NetHack 3.4.3, line 350
- trap.c in NetHack 3.4.3, line 335
- do.c in NetHack 3.4.3, line 1194
- Objects at all: trap.c, line 364 or do.c, line 1032; chance: dokick.c, line 1202
- do.c in NetHack 3.4.3, line 823