An altar, represented by an underscore (_), is a place where you may worship gods. An altar with an aligned priest in the same room is a temple.

Altars and priests are co-aligned if they are of the same alignment as you, or cross-aligned if they are of a different alignment. An altar is aligned if it has lawful, neutral, or chaotic status. Altars of Moloch are unaligned. Unaligned altars do not appear in the main dungeon (except as mimics), only in Gehennom and some quests.

Altars not located in temples are scattered randomly throughout the dungeons. The Valley of the Dead has an unaligned altar located in the temple of Moloch, and Minetown is guaranteed to have an aligned temple altar (both: unless it was destroyed in a bones file).

Altars can be used to detect the BUC status of items. This is done by dropping the item onto the altar. A black flash marks a cursed item and an amber flash a blessed one. You can not detect the BUC status if you are blind. You can not detect whether an item is blessed or cursed if you are hallucinating, as you will not be able to distinguish between amber flashes and black flashes; you can, however, still identify uncursed items, as there will not be a flash at all.

If you #sit on, engrave, or kick an altar, it will lower your luck. This can be used to deliberately lower your luck to prevent crowning. If the altar is of your alignment, it will reduce Wisdom by one point instead, indicated by the message "You feel foolish!". Interestingly, this does not break atheist conduct.

If you (or a monster) [z]ap a wand of digging downwards, you get the message "The digging ray is ineffective" and nothing further happens. However, if you break a wand of digging or apply a drum of earthquake while standing on an altar, it will be destroyed (unless it is a high altar).

Standing on an altar scares V vampires as if you were standing on Elbereth or a scroll of scare monster[1]. Any altar will have this effect, including an altar to Moloch.

Sacrificing corpses[]

You can #offer fresh corpses to your god by sacrificing them on an altar. The greater the monster's difficulty, the more your god will appreciate it. You can gain powerful gifts from sacrifices and may convert opposed altars. Additionally, sacrificing will tell you if your prayer timeout has expired.

The details of the effects of sacrifice follow. Obviously, whatever the outcome of the sacrifice, you lose the atheist conduct.[2] If the corpse is a cockatrice and your hands are bare, you suffer the effects of touching it, even if it wasn't in your inventory.[3]

Further effects depend on the details of the sacrifice.

Ordinary sacrifice[]

This applies to sacrifices made on your own god's altar that are not of your own race, not a pet, not a unicorn, and not made in the endgame.

If the creature is not an acid blob and is greater than 50 turns old (after adjustments for ice), it is rejected: "Nothing happens."[4] (Yes, acid blobs are special: they never expire for sacrifices, although of course they may rot like most food.) Other creatures have a particular value depending generally on their difficulty (see Anger#Value_of_corpses). In some special cases, the value may be negative if the offering displeases your god: see below. Partially-eaten corpses normally get their value decreased by roughly the percentage that's been eaten. For lawful or neutral characters, undead have an extra point of value,[5] but this is only relevant to wraiths, since other undead's corpses are automatically aged too much to sacrifice them.

If your god is angry at you, his anger is decreased by 1/8 the value of the sacrifice, if you're non-chaotic; otherwise, by 1/12 the value of the sacrifice (chaotic gods are harder to appease).[6] The decrease in anger is always rounded down. If your god's anger has been reduced to zero, you'll receive the message that he "seems mollified" (if hallucinating, "seems astral (not a new fact)"), and your luck will be increased to zero if negative. If anger is reduced but not to zero, you'll receive the message that your god "seems slightly mollified" ("seems groovy" if hallucinating), and your luck will be increased by one point if negative. If anger has not been reduced at all, "You have a feeling of inadequacy" (if hallucinating, "The gods seem tall").

If your god is not angry at you, but your alignment is negative, your alignment is increased by the value of the sacrifice, up to a maximum of 0 alignment, and "you feel partially absolved".[7]

Otherwise, if your prayer timeout is greater than zero, it's decreased by 12.5 times the sacrifice's value if you're lawful or neutral, or 125/6 (about 20.8) times its value if you're chaotic, obviously to a minimum of zero. If this decreases your prayer timeout to 0, then "you have a feeling of reconciliation" (if hallucinating, "Overall, there is a smell of fried onions"), your luck is increased to zero if negative, and it's safe to pray. If your prayer timeout is not yet zero, "You have a hopeful feeling" (if hallucinating, "You realize the gods are not like you and I"), your luck is increased by one if negative, and it is not yet safe to pray.[8]

If none of the above apply, you generally have a chance of getting an artifact. Your level must be greater than 2, and your luck must be nonnegative. If those conditions are met, the chances of your getting an artifact are 1/(10 + 2×number of artifacts that exist×number of gifts granted by your god). If you do receive an artifact, you'll get the message "An object appears at your feet!", and your god will tell you to "use my gift wisely!" You exercise your wisdom, your prayer timeout is set to 300 + 50×the number of artifacts that exist, and your skill in using the artifact's type of weapon becomes unrestricted.

Whether or not you get the artifact, your luck increases by 5/24 (about 20.8%) the value of the sacrifice, and is set to 0 if still negative. You receive the message "You glimpse a four-leaf clover at your feet" (if hallucinating, "You see crabgrass at your feet. A funny thing in a dungeon"). This luck bonus occurs even if you're below level 3 or have negative luck, but not if you had an angry god, negative alignment, or nonzero prayer timeout.


You must be at least level 3 to receive gifts. Your first gift will be an aligned artifact that does not hate your current form. Some roles have a guaranteed first sacrifice gift, which is noted below; its alignment will be adjusted to your starting alignment if necessary.

If at least one aligned artifact has already been given, then unaligned ones also become eligible[9].

Lawful Gifts: Demonbane, Grayswandir, Snickersnee (Samurai), Sunsword

Neutral Gifts: Cleaver (Barbarian), Giantslayer, Magicbane (Wizard), Mjollnir (Valkyrie), Vorpal Blade

Chaotic Gifts: Grimtooth, Orcrist, Sting, Stormbringer

Unaligned Gifts: Dragonbane, Fire Brand, Frost Brand, Ogresmasher, Trollsbane, Werebane

Variants may have different rules, in particular, many new SLASH'EM artifacts.

Sacrificing creatures of own race[]

If the creature you sacrifice is of your own race, basically, you get good effects if you're chaotic, bad effects otherwise:

  • If you are chaotic, you gain five alignment.[10] If you are a demon, you exercise your wisdom. If the altar is chaotic, you gain two luck,[11] and if the altar is unaligned, you lose two luck. Your luck is unaffected if the altar is lawful or neutral.
  • Whatever the altar is, if you're non-chaotic, you abuse your wisdom,[12] you lose 5 alignment, your god's anger increases by three, your wisdom decreases by one point, your luck decreases by 5, and outside of Gehennom, your god will punish you as for praying too much (depending on the level of anger).[13] Finally, if the altar is chaotic, you'll destroy it and anger any attendant priest.[14]
  • If the altar is lawful or neutral, it will be immediately converted to chaotic – independently of the hero's alignment. This will anger any priests but apparently not suffer the other effects of conversion.[15]
  • If the altar is chaotic or unaligned, a demon will be summoned under some circumstances. The demon will be peaceful if you are chaotic and hostile otherwise. The first two demons will be Juiblex and Yeenoghu in any order, followed by foocubi.[16]

No further effects occur in this case. Oddly, this means that chaotic characters may wish to sacrifice creatures of their own race even at Moloch's altar, if they prefer +5 alignment and -2 luck for some reason. The check for same race is done before the check for a former pet and ignores the check for age, so same-race corpses are always fit for sacrifice until they rot away completely.

Keep in mind that werecreatures are considered human, so sacrificing them if you're human will have the consequences described above.

Sacrificing pets[]

Sacrificing pets (specifically, creatures that died while tame) will generally cause you to lose three alignment and gain the aggravate monster intrinsic.[17] The pet will have a sacrificial value of -1, causing it to worsen certain things that generally benefit from sacrifice (unless at a cross-aligned altar). It proceeds as an ordinary sacrifice. Former pets that have gone feral no longer count as pets, and may be killed and sacrificed as usual.

Cross-aligned altars[]

You can convert cross-aligned altars by sacrificing at them if they're not in Gehennom. If you fail, you will lose 1 Luck and possibly have monsters sent in to defend the altar. If you succeed then you gain 1 Luck and the altar becomes coaligned. The chances to convert an altar go up with character level. Note that attempting to convert an altar with a priest present is a Bad Idea.

If you are a non-chaotic human, do not make the mistake of sacrificing a cross-aligned priest at the altar in her own temple. Just like any other instance of sacrificing your own race, that will anger your god, and will never convert the altar to your alignment.

The probability to convert an altar is: (YourLevel+2)/(YourLevel+8)

Level 2 / Level 8

When attempting to convert an altar, you will get the message "You sense a conflict between <your god> and <the god of the altar>". A successful conversion will produce the message "You feel the power of <your god> increase", while a failed one will result in "Unluckily, you feel the power of <your god> decrease."

A sacrifice with negative value, such as an altar-aligned unicorn or a former pet, will not cause an attempted conversion. Instead, it will anger the altar's god, which will actually decrease your own god's anger by one.[18] You will still suffer the usual effects of angering a god, including the loss of any divine protection and being smitten by the angry god.

Danger in sacrificing[]

Sacrificing can be dangerous in the following circumstances:

  • Sacrificing at an altar not of your alignment type (ie. Lawful, Neutral, Chaotic) when your alignment is negative.
    • This may convert you to the altar's alignment, you lose 3 luck, and your prayer timeout increases by 300. Note that if this happens before you have been admitted to the quest, the game will be unwinnable.
    • If your god is angry with you, but your alignment is positive, you will not be converted.
  • Sacrificing at an altar not of your alignment type (ie. Lawful, Neutral, Chaotic) when your alignment is high and you are at least level 7.
    • This might convert the altar but may summon a minion of the altar's original god. The probability varies, but is never greater than 1/4. The probability is higher in NetHack brass and SLASH'EM, see #Variants.
    • Additionally, if you do this to convert an altar in a temple with attending priest, the priest will become angry at you.
  • Sacrificing your pets.
    • You lose 3 alignment and gain the aggravate monster intrinsic.
    • If sacrificed to your god, you also gain 1 anger, and your god will smite you.
    • If sacrificed to another god, you lose 1 anger, and that god will smite you.
  • Sacrificing your own race if you are not chaotic.
    • You lose 5 alignment and 5 luck, and your god's anger increases by 3. On a chaotic altar, this will summon a hostile demon lord or other major demon. Other altars are converted to chaotic.
    • If not in Gehennom, your god will also smite you.
  • Sacrificing a unicorn on an altar of its own alignment.
    • You lose 1 wisdom.
    • If coaligned altar, you gain 1 anger, and your god will smite you.
    • Otherwise, you lose 1 anger, and the altar's god will smite you.
  • Sacrificing a unicorn of your alignment at a non-coaligned altar.
    • You will convert to the altar's alignment if you have never been converted before.
    • Otherwise, you gain 3 anger, lose 5 alignment, lose 2 wisdom, lose 5 luck, and if not in Gehennom your god will smite you.
  • Sacrificing at an altar of Moloch while in Gehennom (e.g. at the Valley).
  • Sacrificing at the high altar of Moloch (in the Sanctum).
    • You are hit by a bolt of lightning and wide-angle disintegration beam, and die if not shock/disintegration resistant.
  • Sacrificing anything but the Amulet of Yendor at a cross-aligned high altar.
    • You are hit by a bolt of lightning and wide-angle disintegration beam, and die if not shock/disintegration resistant.
    • If you survive, the god will summon 3 hostile minions.

Sacrificing unicorns[]

Sacrificing unicorns is tricky because the altar's alignment, your alignment, and the unicorn's alignment all factor into the outcome.[19] A unicorn's alignment is represented by its color. The white is lawful, grey neutral, and black chaotic. The points to remember are:

  • Never sacrifice a unicorn on an altar of its own alignment; "such an act is an insult to {law|balance|chaos}!" You lose one point of wisdom and the altar's god becomes angry – with the same effect as angering that god through prayer [20]. If the altar is not of your alignment, your god's anger is reduced by one[21].
  • Never sacrifice a unicorn of your alignment. This increases your god's anger by one and acts as above if the altar is also of your alignment. If the altar is cross-aligned, this will set your alignment score to -1, which makes your sacrifice convert you instead of the altar.
  • If you have already been converted once before then an attempted conversion sacrifice will be rejected by the altar's deity (-5 to luck and alignment score, -2 to wisdom) and you will anger and be punished by your current deity.

Each time you sacrifice a unicorn of a different alignment on your own altar, you get a +5 boost to your alignment and the message "You feel appropriately {lawful|neutral|chaotic}", or "You feel you are thoroughly on the right path" if alignment is at maximum.

The rest of the effects are summarized in the following table:

You Unicorn Altar Effect
Lawful.pngLawful Lawful.pngWhite Lawful.pngLawful Bad
Lawful.pngLawful Lawful.pngWhite Neutral.pngNeutral You become neutral
Lawful.pngLawful Lawful.pngWhite Chaotic.pngChaotic You become chaotic
Lawful.pngLawful Neutral.pngGrey Lawful.pngLawful Good
Lawful.pngLawful Neutral.pngGrey Neutral.pngNeutral Bad
Lawful.pngLawful Neutral.pngGrey Chaotic.pngChaotic Attempt to convert altar
Lawful.pngLawful Chaotic.pngBlack Lawful.pngLawful Good
Lawful.pngLawful Chaotic.pngBlack Neutral.pngNeutral Attempt to convert altar
Lawful.pngLawful Chaotic.pngBlack Chaotic.pngChaotic Bad
Neutral.pngNeutral Lawful.pngWhite Lawful.pngLawful Bad
Neutral.pngNeutral Lawful.pngWhite Neutral.pngNeutral Good
Neutral.pngNeutral Lawful.pngWhite Chaotic.pngChaotic Attempt to convert altar
Neutral.pngNeutral Neutral.pngGrey Lawful.pngLawful You become lawful
Neutral.pngNeutral Neutral.pngGrey Neutral.pngNeutral Bad
Neutral.pngNeutral Neutral.pngGrey Chaotic.pngChaotic You become chaotic
Neutral.pngNeutral Chaotic.pngBlack Lawful.pngLawful Attempt to convert altar
Neutral.pngNeutral Chaotic.pngBlack Neutral.pngNeutral Good
Neutral.pngNeutral Chaotic.pngBlack Chaotic.pngChaotic Bad
Chaotic.pngChaotic Lawful.pngWhite Lawful.pngLawful Bad
Chaotic.pngChaotic Lawful.pngWhite Neutral.pngNeutral Attempt to convert altar
Chaotic.pngChaotic Lawful.pngWhite Chaotic.pngChaotic Good
Chaotic.pngChaotic Neutral.pngGrey Lawful.pngLawful Attempt to convert altar
Chaotic.pngChaotic Neutral.pngGrey Neutral.pngNeutral Bad
Chaotic.pngChaotic Neutral.pngGrey Chaotic.pngChaotic Good
Chaotic.pngChaotic Chaotic.pngBlack Lawful.pngLawful You become lawful
Chaotic.pngChaotic Chaotic.pngBlack Neutral.pngNeutral You become neutral
Chaotic.pngChaotic Chaotic.pngBlack Chaotic.pngChaotic Bad

Note: You will lose any intrinsic protection whenever your alignment changes.

Prayer timeouts and sacrifice[]

Sacrificing on an altar reduces your prayer timeout and you get a message indicating the status of your prayer timeout.

"You have a hopeful feeling."
You may not pray yet because your prayer timeout hasn't expired.
"You have a feeling of reconciliation."
You may pray because your sacrifice reduced your prayer timeout to zero.
"An object appears at your feet!"
You may not pray because you received a gift and your prayer timeout has been increased.
"You have a feeling of inadequacy."
You may not pray. Your god is still angry at you; your sacrifice did nothing to reduce his anger.
"<Deity> seems slightly mollified."
You may not pray. Your god's anger has been reduced but it is not yet zero.
"<Deity> seems mollified."
You may pray because your god's anger has been reduced to zero.
"You feel partially absolved."
You may not pray because your alignment was negative, and has been increased by the level of the corpse, to a maximum of zero. Sacrifice again to find if it's safe to pray.
"You glimpse a four-leaf clover at your feet."
Your luck was increased; you may pray.
"You think something brushed your foot."
Your luck was increased while blind; you may pray.
"You see crabgrass at your feet. A funny thing in a dungeon."
Your luck was increased while hallucinating; you may pray.
"Your sacrifice is consumed..." and no further message
You may pray

Making water holy/unholy[]

If you drop one or more potions of water onto an altar and #pray, the potions become blessed if the altar was aligned with you and become cursed if the altar was not aligned with you. This occurs regardless of whether the water was blessed or cursed before. Be aware that water praying on a cross-aligned altar will anger your god, decrease your luck, and you might be punished in some other way.

Normal prayer timeouts apply when praying on altars.


It is possible to survive indefinitely on a level with an altar. Under normal circumstances, the need for food drives you to deeper unexplored levels. However, you can instead pray when weak, and sacrifice to reduce your prayer timeout back to zero. Doing this for extended periods of time can net you many death drops, and a collection of gifts from your god if your luck is substantially high. This is considered by some as degenerate. It is most effectively done with black puddings , which is known as "pudding farming".

High altars[]

The three altars on the Astral Plane and the altar in Moloch's Sanctum are considered to be high altars. They act largely as normal altars, but cannot be converted under any circumstances; doing so will cause the god in question to attempt to zap you and, failing this, will summon three minions to protect the altar. In addition, it is not possible to sacrifice monsters unless you are holding them, to stop you sacrificing the riders.

To correctly ascend, one must #offer the real Amulet of Yendor (held in main inventory, NOT dropped on the altar) at the altar of your alignment. Determining the alignment of the altar requires standing on its location and using the : look command. The ; farlook command does not give information about a high altar's alignment. Another method for detecting the correct altar is noticing if you are given sanctuary; that is, all monsters, other than the Riders, aligned priest, and angelic beings, will not be allowed to enter and cannot attack you with melee attacks.


Randomly generated altars appear in ordinary room and corridor levels. There is an independent 1 in 60 chance of each room containing an altar, provided that room is not a Special room.[22] The altar has an equal probability of any one of the three alignments. Altars will not be generated adjacent to doors (diagonal is ok), but otherwise could occupy any spot in the room not already occupied by something else.[23] The chance of an empty room containing an altar does not change with dungeon level.

Encyclopedia entry[]

Altars are of three types:
1. In Temples. These are for Sacrifices [...]. The stone
top will have grooves for blood, and the whole will be covered
with _dry brown stains of a troubling kind_ from former

[ The Tough Guide to Fantasyland, by Diana Wynne Jones ]

To every man upon this earth
Death cometh soon or late;
And how can man die better
Than facing fearful odds
For the ashes of his fathers
And the temples of his gods?

[ Lays of Ancient Rome, by Thomas B. Macaulay ]


Players of NetHack brass and SLASH'EM need to be wary when converting altars, because of the increased chance that the altar's original god will dispatch a minion against you. At experience level 7 or above with high alignment, the chance of a minion appearing after converting the altar is the same as vanilla.[24] As in vanilla, the god will yell, "Thou shalt pay for thy indiscretion!"[25] Players with a high luck will have fewer minions dispatched against them.

Even worse, there's an additional chance of one or more minions appearing post-conversion. In SLASH'EM, if you are at experience level 4 or above, there is a chance that "You feel (god) is very angry at you!" and the god dispatches two minions.[26] Afterwards, you still have the original chance of another minion, as above. Again, luck is a factor.

In NetHack brass, you will always receive "You feel (god) is very angry at you!" For all experience levels, at least one minion will appear. Two rolls are made: the first from 0 to 9, the second from 0 to 19. For each roll, if your level is greater than the generated random number, a post-conversion minion is summoned. Luck is not a factor. Thus in brass it is very dangerous to convert altars. You might convert an altar at experience level one and have to flee to another level from one minion, or three minions if the game rolled 0 twice, thus giving you no use of the converted altar. If converting an altar at experience level 7 or above, you might still get the pre-conversion minion, forcing you to fight as many as four summoned minions.[27]

Source code references[]