Luck
~~~~
Partly quoted from the "gems-322.txt" spoiler by Kevin Hugo, and partly
from Roy Stead's "NetHack A-Z".
Collected for NetHack 3.2.3 by Jonathan Ellis.

Your luck affects many aspects of the game (too many to mention here),
and is actually the sum of two components.  Base luck changes with events
in the game, and may slowly return to a "baseline" level - in no case can 
it go above 10 or below -1, whatever you do. Bonus luck, on the other hand,
is determined by what kind of luckstone (and certain artifacts) you are 
carrying.  You can determine your total luck by quaffing a noncursed potion
of enlightenment, ending the game and asking to see your attributes, or in 
debug mode - the messages are shown here:

  TOTAL LUCK  MESSAGE
  ~~~~~~~~~~  ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
     = -10    extremely unlucky
   -9 to -5   very unlucky
   -4 to -1   unlucky
       0      luck is zero (debug mode only)
    1 to 4    lucky
    5 to 9    very lucky
     = 10     extremely lucky

Your bonus luck -- and whether your base luck will return to its baseline
level -- is controlled by luckstones and certain quest artifacts.  The
effect of these "luck-items" depends on the number in your main inventory
that are blessed, uncursed, and cursed (see table below).  Note that you
can't do any better than one blessed luck-item, so you might as well keep
any others in a bag (where they have no effect) as spares in case your
main one is cursed. (Luck items carried in a bag have no effect on the 
character.)

  NUMBER OF LUCK-ITEMS        BAD LUCK    GOOD LUCK   BONUS LUCK
  ~~~~~~~~~~~~~~~~~~~~        ~~~~~~~~    ~~~~~~~~~   ~~~~~~~~~~
  None                        Times out   Times out   0 (no message)
  More cursed than blessed    No timeout  Times out
  Equal cursed and blessed    No timeout  No timeout
  More blessed than cursed    Times out   No timeout
  More cursed than noncursed                          -3 "reduced luck"
  Equal cursed and noncursed                          +3 "extra luck"
  More noncursed than cursed                          +3 "extra luck"
When you are enlightened about your luck, you are also told if you have
bonus luck and if good/bad luck will not time out.

Base luck is adjusted by each of the events described below.  It cannot
be reduced below -10 or increased above +10.  In addtition, every 300
turns (or 600 if you have the Amulet of Yendor or have angered your god),
your luck will increase by one if it is less than your baseline luck and
bad luck times out, and your luck will decrease by one if your luck is
greater than your baseline luck and good luck times out.  Your baseline
luck is +1 if you started or restored the game during a full moon, -1
if started/restored on Friday the 13th, and 0 if neither or both.

  BASE ADJ  EVENT
  ~~~~~~~~  ~~~~~
     +1     Starting or restoring a game during a full moon.
      0     Starting or restoring a game during a new moon.
     -1     Starting or restoring a game on Friday the 13th.
            NOTE: The above three are reversed before saving.
     -2     Breaking a mirror.
     -n     Breaking n hatchable eggs (at worst -5).
     +1     Sitting on a throne (sometimes).
      0     Throwing a worthless gem at a unicorn - whether identified, 
            named or unknown.
  -1 to +1  Throwing unknown or named but unidentified valuable gem at
            a non-coaligned unicorn.
  -3 to +3  Throwing identified valuable gem at a non-coaligned unicorn.
     +1     Throwing unknown valuable gem at coaligned unicorn.
     +2     Throwing named valuable gem at coaligned unicorn.
     +5     Throwing identified valuable gem at coaligned unicorn.
     -1     Hitting a blind floating eye (1 in 500 chance).
     -1     Killing a tame or peaceful (sometimes)  monster.
     -2     Killing a peaceful human, and you are not chaotic.
     -5     Killing a coaligned unicorn.
  -5 to -2  Cannibalism (eating your own species).
  Set to 0  Praying with negative luck (sometimes; need to be in trouble).
     -3     Praying on wrong altar.
     -3     Praying before your prayer timeout has expired.
     -5     A sacrifice (not your own race) on Moloch's altars.
     -3     Being converted by trying to convert an altar.
     -1     Otherwise unsuccessful at converting altar.
     +1     Successfully converting an altar.
     -1     Desecrating another god's altar.
     +2     Sacrificing your own race on your own chaotic altar.
     -2     Sacrificing your own race on Moloch's altar.
     -5     Sacrificing your own race, you aren't chaotic.
     -1     Sacrificing an unidentified fake Amulet of Yendor.
     -3     Sacrificing an identified fake Amulet of Yendor.
     +1     Sacrificing, slightly mollifying your god, negative luck.
  Set to 0  Sacrificing, mollifying your god, negative luck.
     +1     Sacrificing, having a hopeful feeling, negative luck.
  Set to 0  Sacrificing, reconciling, negative luck.
  +1 to +5  Sacrificing, god happy.

Other effects of luck on your game
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

If you are lucky, you have a greater chance of good effects when dealing 
with thrones, whether kicking or sitting on them. Luck can affect the following
things, in small or big ways:

 - the chance of items found on the floor being blessed or cursed
 - your chances or succesfully writing a spell or spellbook on a blank 
   scroll or spellbook
 - your chance of getting gold or gems (with good luck) or destroying a throne 
   (with bad luck) by kicking it
 - finding secret doors, passageways and traps when searching
 - the severity of the effects of being trapped
 - your chances of hitting a monster
 - your chance of opening a closed door or shutting an open one
 - your chance of getting exactly what you want when you wish, or indeed
   anything at all in the case of really bad luck
 - your chance of getting a wish from sitting on a throne
 - the likelihood of your scrolls and potions being blanked and diluted by 
   stepping into water
 - your chance of successfully casting a spell
 - the chances of your weapon being affected by rust when you trigger a rust 
   trap, if your weapon can rust.
 - and possibly other things as well.