# Bones
A bones level is a level that is saved when you die, which may be reloaded into some future game. Such levels are also known as bones files or simply bones.
The game will store no more than one bones file per dungeon level. When a player enters a level for the first time and a bones file exists for that level, it will only be loaded as a bones level 1⁄3 of the time;[1] otherwise, it will generate the usual level and the bones file will remain untouched. 
Bones levels can be a double-edged sword: the bones pile they contain will have all the dead adventurer's possessions, but if they were killed by a monster it will still be present. If a second adventurer is killed in a bones level, the level may then again be saved as bones, creating a double bones; in some cases, a triple or even a quadruple bones is possible.
As of NetHack 3.6.1, some traps in the earlier dungeon levels may be generated with a pre-aged corpse and a few cursed items on top of them; these are designed to simulate the "bones" of the trap's unfortunate victims. This does not occur with entirely non-lethal traps such as squeaky boards.

Contents

1 Creation
2 Clues
3 Strategy
4 Forensics

4.1 Item identification

4.1.1 Identification via the class of the deceased

5 Substitutions
6 Ethics
7 Bones files locations
8 Wizard mode
9 Variants

9.1 dNethack
9.2 FIQHack

10 References
11 See also

Creation
If you die in an eligible level, the chance of leaving bones is:
[2]
This means that the chance of leaving bones at DL 1–3 is 0%, DL 4–7 is 50%, DL 8–11 is 67%, DL 12–15 is 75%, DL 16–19 is 80%, etc.
Ineligible levels for leaving bones include the following:[3]

The first three levels of the dungeon, as shown above
The first level of the Gnomish Mines, if it is at DL 3. (However, you can still load bones anywhere in the mines.)
Mines' End
Sokoban
The Quest Home and Quest Goal levels
Fort Ludios
Medusa's Island
The Castle
Vlad's Tower, top and bottom (but the middle level is eligible)
The Wizard's Tower, top and bottom (but the middle level is eligible)
Fake Wizard's Tower, with portal
The level containing the vibrating square
Moloch's Sanctum
The Elemental Planes
The Astral Plane
Any level with a portal (to the quest, Fort Ludios, or the Wizard's Tower)
Any level with stairs leading to multiple different branches
Bones files in eligible special levels, such as Minetown, may be loaded as bones at a different level than they were saved at, sometimes breaking other ad-hoc rules like 'no polymorph traps above dungeon level 8'.

Clues
Some things that may indicate that a level is a bones level:

An abnormally large concentration of different monsters.
Wounded monsters (can be identified with a stethoscope, but note that ordinary traps can also wound monsters).
Broken doors (can be identified with far look).
Unusual holes in walls (but they may also be created by a tunneling monster, especially if there are tunnels containing rocks nearby).
Empty or partly empty throne rooms, zoos, leprechaun halls, or other special rooms.
Engraved messages other than those randomly placed by NetHack.
Few to no items lying on the floor.
Suspicious or unusual items around the level. For example, disarmed bear traps are never generated randomly.
Containers with contents unlike those randomly generated, such as weapons and armor.
Piles of items related to specific monsters. A collection of quarterstaffs or leather armors, or even a noticeable number of elven, dwarvish, or orcish items can indicate that some combat has occurred on the level before you arrived.
A ghost, in a room other than a graveyard. Note that bones ghosts will always be named after the dead player, and a ghost with one of the random names does not indicate bones. Also, a few special levels generate one random ghost when they are created; this also does not indicate bones.
A named mummy, wraith, vampire, or green slime.
Named monsters.
Monsters which should not be generated for this particular level or at your current difficulty (for example, an archon on DL4).
Presence of corpses, which are never randomly generated, except in the Valley of the Dead, Orcish Town, and on top of traps in the first four levels of the Dungeons of Doom or behind iron bars. (Corpses might also be caused by random monsters dying to traps.)
Presence of fruit (slime mold) with a different name from the one you set. This is a dead giveaway.
Strategy
A bones level will contain some remnant of the player whose bones are laying about. Typically this is a ghost bearing the name of the player, which will be sleeping over the bones pile unless something woke it up. 
Depending on what the player was killed by, a monster other than the ghost will appear:

If the player was killed by any V (vampire, vampire lord, or Vlad), a named (regular) vampire replaces the ghost.
If the player was killed by any W (wraith, barrow wight, or Nazgul), a named wraith replaces the ghost.
If the player was killed by a ghoul, the ghost is replaced with a ghoul.
If the player was killed by a mummy, the ghost is replaced with the appropriate mummy (human mummy, elf mummy, etc.)
If the player was killed or petrified by a footrice, there is a statue of the player instead, even if the player did not die by stoning.
Killing or luring the ghost or monster away gives you access to the bones pile, which contains the entire inventory of the player when they died. Every item in the bones pile has an 80% chance of being cursed outright, and a 20% chance of retaining its original BUC. It is thus usually a bad idea to quaff, read, wield, or wear anything from a bones pile until it has been properly BUC identified.  Turning off autopickup temporarily before you step onto the bones pile is a good idea, so you can look through the items at your leisure and don't accidentally encumber yourself by picking up many items at once.
If there is a bag in the bones pile, it may be a bag of holding (unless the adventurer appears to be an early Rogue or Archeologist, in which case it's probably just a sack). Since the bag may be cursed, it might not be wise to loot it on the spot and risk destroying its contents. Try to lift it; if you find it very difficult or impossible, it is likely a cursed bag of holding. If you can get it into your inventory, you can treat it with a scroll of remove curse or dip it in a potion of holy water. If not, you can zap a wand of cancellation at it on the floor to uncurse it. As a last resort, you can tip it.
Beware! The original killer is still lurking about the level, probably not too far from the site of the bones. If you discover a bones pile with very advanced items, be very careful about running into whatever managed to kill your predecessor! A headstone generates under the bones pile; this means that you can't engrave Elbereth on that square to keep monsters from attacking you while you sort through it. If you need to fight, step into another square. Alternatively, stand on top of a scroll of scare monster. (There might even be one in the bones pile already.)
On the other hand, you want to get at any wands of fire or lightning the player may have been carrying before monsters can use them against you. Luckily, the ghost on top is generated asleep and will prevent other monsters from moving onto the pile until you wake it up.

Forensics
Item identification
Objects that the deceased player has #named will be reset to whatever description that object has in the current player's game. In other words, if the deceased had a yellow potion named "this burns when thrown" (meaning it was acid), but acid in the current player's game is a purple potion, the potion will show up as purple, without a name. The exception to this rule is fruit, which retains its name in bones piles. Thus, naming your fruit "Look out for the master mind flayer!" is a clever dying action to inform the next player about your demise. Engraving is a more restrictive method of issuing such warnings, as you can only engrave a maximum of eight characters per turn, which limits your final vocabulary to phrases like "purple&nbsp;h", "GWTWOD", or "Archon".
Assuming that the game is being played on a public server that provides dumplogs, the less scrupulous may look up the dumplog to see what items were carried. As these logs include an ASCII image of the game map at time of death, determining which of the logs belongs to the body you found is simple. This is probably cheating, though, and some players frown upon it.

Identification via the class of the deceased
When encountering a bones level, it can be advantageous to know some details of the deceased, or at least his or her class. For example, if you find a grave with a quarterstaff, a randomly named cloak, two spellbooks, and a magic marker, you can be fairly certain the corpse is that of an early wizard, from which you can deduce that the cloak is a cloak of magic resistance. This method comes with no guarantees, but the more "indicator items" you find, the more certain you can be.

Class

is indicated by

Archeologist

bullwhip, fedora, tinning kit

Barbarian

two-handed sword, battle-axe

Caveman

large number of rocks and/or flint stones

Healer

scalpel, stethoscope

Knight

lance, many apples and carrots, saddle (possibly on a horse)

Monk

many apples and oranges, a robe

Priest

4 potions of water, both of: mace and robe

Ranger

two large stacks of arrows

Rogue

large stack of daggers, sack, lock pick

Samurai

large stack of ya (bamboo arrows), katana and short sword

Tourist

Hawaiian shirt, expensive camera, credit card, stack of 4 scrolls

Valkyrie

long sword, small shield, dagger

Wizard

quarterstaff, randomly named cloak, two spellbooks, two rings, a few scrolls and potions, one wand

Rogues and Valkyries are hard to identify, since they both start with items common to other classes, or commonly generated.  A +3 small shield almost certainly used to belong to a Valkyrie, but to determine the enchantment, you need to either identify or try on the shield.

Substitutions
The following items will be substituted upon a save:

Died with

Saved with

Amulet of Yendor

cursed cheap plastic imitation of the Amulet of Yendor

Candelabrum of Invocation

cursed, used, unlit wax candle

Bell of Opening

cursed bell

Book of the Dead

cursed spellbook of blank paper

Upon loading, the following artifacts are changed to their base type:

Your quest artifact
Any artifact that was already created in your game
Note that the alignment of any quest artifact is not affected by the alignment of the deceased: if the Mitre of Holiness is found in bones, you will be unable to grasp it unless you are lawful, even if it was retrieved from Nalzok by a chaotic priest.
Additionally, certain monsters will never be saved in bones:[4]

Medusa
the Wizard of Yendor
Vlad the Impaler
your quest nemesis
your quest leader
Their statues and corpses are unaffected (bug C342-54), but upon revival, will turn into doppelgangers.[5]
Tame monsters will turn hostile.[6]

Ethics
Using bones items in a normal game is perfectly fine. Bones can often make a difficult game much easier by providing items that the current player has not "earned" yet. If you are going for some record, especially a speed run, the ascension is likely more impressive if not using bones items at all.
From a game design point of view, bones are potentially unbalancing, and a few players object to using bones items for this reason. Finding one's own bones is an even more difficult position. Luckily on a public server there are enough players that this is unlikely to happen too frequently.
If the deceased player's dumplog is available, it can be used to identify items in the bones pile. This could be considered cheating. Many players do it, but endless debates rage on RGRN about the value of such wins. Please disclose dumplog usage.

Bones files locations
On the Windows port, the data for a bones file is stored in the playground directory. As the filename contains clues to where the player died, it is trivial to identify potential bones levels. The file is created when a player dies on a bones-capable level and is deleted when a bones level is reached and incorporated in to an active game. If the player later dies on a bones-capable level, the file may be re-created with the appropriate filename.
Thus, if the player observes the files within the playground, they can notice when a suitable level is coming up, and notice if the file is deleted, and thus know that they are on a bones level.
The file naming format that is used is "bon

<branch><role>.<level>", for example "bonM0.T" is the bones file for Minetown.
Within the filename, <branch> is one of:

D – Dungeons of Doom
M – Gnomish Mines
G – Gehennom
T – Vlad's Tower
Q – Quest
And <role>:

Is normally "0", if part of the normal dungeon
Changes to "Bar" for Barbarian, "Wiz" for Wizard etc - specific branches for quests. In SLASH'EM, can also be "Law", "Neu" and "Cha" for the alignment quests.[7]
And <level> is one of:

Numbers 1 through 53 – ordinary levels eligible for leaving bones (this number is offset from the first of the branch appropriate—e.g. if the bones are on the second level of the mines, the filename would be "bonM0.2")
O – Oracle (if <branch> is "D", as the Oracle can only be in the Dungeons of Doom and Orcus Town shares "O")
T – Minetown
R – Rogue level
V – Valley of the Dead
A – Asmodeus' Lair
B – Baalzebub's Lair
J – Juiblex's Swamp
O – Orcus Town (if <branch> is "G", as Orcus Town can only be in Gehennom and the Oracle shares "O")
X – Wizard's Tower
N – Nymph level (exists in SLASH'EM and UnNetHack)
The file is not designed to be human-readable. The characters corresponding to each level and branch are defined in dungeon.def.

Wizard mode
In wizard mode, you will be prompted when you reach a bones level with the message "Get bones? [yn] (n)", allowing you to selectively retrieve the bones file for that level. You'll also get the prompt "Unlink bones? [yn] (n)". Selecting y removes that bones file from the possible set of bones files for normal games.
When you die on a bones-suitable level, you will be presented with the opportunity to "Save bones? [yn] (n)", again allowing you to selectively save bones files. If there was already a bones file for that level (i.e. you said no to getting bones when entering a level) you will also be prompted with "Bones file already exists. Replace? [yn] (n)", allowing you to selectively overwrite the bones file for that level.

Variants
dNethack
In addition to the above monsters, dreadblossom swarms and shades leave a monster of the same type instead of a ghost if a bones file is created from them killing the player. Dread Seraphs leave skeletons, and gnoll ghouls will leave regular ghouls. Binders will always leave broken shadows (a weaker version of a shade) instead of ghosts in a bones file.
Note that Mammon does not currently leave a golden statue in a bones file.

FIQHack
Bones in FIQHack are more dangerous than in vanilla: the ghost will have the same intrinsics as the deceased character, and there is also a 33% chance that the ghost will be replaced with a player monster that has the same inventory, spells, and intrinsics as the dead character.

A user has suggested improving this page or section as follows:
"Add information about changes introduced in variants (for example UnNetHack)"

References

↑ bones.c in NetHack 3.4.3, line 385: "only once in three times do we find bones"

↑ src/bones.c in NetHack 3.6.6, line 344

↑ no_bones_level in bones.c

↑ bones.c in NetHack 3.4.3, line 226

↑ commit fixing unique monster bones revival

↑ bones.c in NetHack 3.4.3, line 299

↑ files.c in NetHack 3.4.3, line 617

See also
Hearse
Ghost
Options § bones

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It may contain text specific to NetHack 3.6.0. Information on this page may be out of date.
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