Prayer in
Nethack is very useful to get you out of bad situations such as being
weak from hunger or almost
dead, or to create
holy water by praying on your god's
altar. However, praying too often is a Bad Thing because it will anger your god. Newbies occasionally get confused about this and think they are supposed to pray regularly, but in Nethack prayer is pestering your god for help and they don't mind at all if you never pray. (They don't even mind if you never
sacrifice, but they will reward you if you do.)
How can you tell whether it's safe to pray? If you have a means of enlightening yourself, just use it. If there's an altar nearby, you could sacrifice and watch your god's reaction.
Otherwise, these are the criteria. First some minor conditions that are easy to fulfil. You must not be in Gehennom (and the Valley of the Dead counts as Gehennom) or standing on another god's altar. If you are polymorphed into a demon, the very idea of praying to a lawful or neutral god will be repugnant to you. I believe that praying while polymorphed into an undead creature is also unwise.
The conditions which are slightly more likely to cause problems are:
- Your prayer timeout must have expired (if you're in trouble, you can pray slightly before it expires). Remember that wishing and gaining an artifact through sacrifice add to your prayer timeout.
- Your alignment must not be negative.
- Your luck must not be negative (so be careful on Friday the 13th).
- Your god must not be angry with you. Anger doesn't time out; you will have to appease an angry god if you ever want to pray again.