Altar

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

Altars and priests are co-aligned if they are of the same alignment as you, 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, 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. Minetown is also guaranteed to have a temple altar.

Altars can be used to detect the BUC status of items. This is done by dropping the item onto the altar. A dark glow marks a cursed item and an amber glow a blessed one. You can not detect the BUC status if you are blind or hallucinating.

Sacrificing corpses
You can #offer fresh corpses to your god by sacrificing them on an altar. The tougher the monster, the more your god will appreciate it. You can check the experience level of a monster by using a stethoscope on it. Since you have to touch the offering you must be wearing gloves when sacrificing cockatrice corpses. Additionally, sacrificing will give you an indication of your current prayer timeout.

If you are lucky, sacrificing on an altar of any alignment other than your own converts the altar and the power of your god increases. If you are unlucky, the altar may resist, or you might be converted to the altar's alignment yourself. Trying to convert the altar in a temple will anger the priest. Altars in Gehennom are unaligned and cannot be converted. Other unaligned altars in the game, found on some quests, however, can be converted.

Danger in sacrificing
Sacrificing can be dangerous in the following circumstances:
 * Sacrificing at an altar of Moloch.
 * You gain 3 anger, lose 5 alignment, lose 2 wisdom, lose 5 luck, and get a negative effect.
 * 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.
 * 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 will convert the altar but may summon a minion of the altar's original god. The probability varies, but is never greater than 1/4.
 * Sacrificing former pets.
 * You lose 3 alignment and gain the aggravate monster intrinsic.
 * Sacrificing your own race.
 * This can summon a named demon, which will be hostile if you are not chaotic.
 * Sacrificing a unicorn on an altar of its own alignment.
 * Sacrificing a unicorn of your alignment.

Sacrificing your own race
It is considered bad for a human or an elf to sacrifice corpses of their own race. Doing so will cause wisdom, luck, and alignment to be abused. However, chaotic characters can do this safely. Doing so will cause a peaceful demon lord to be summoned while luck and alignment are exercised.

Sacrificing unicorns
Sacrificing Unicorns is tricky because the altar's alignment, your alignment, and the unicorn's alignment all factor into the outcome. 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.
 * Never sacrifice a unicorn of your alignment.

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

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

Making water holy/unholy
If you drop a potion of water or several 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 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.