Nethack Protection Spoiler

This HTML document is hereby placed in the public domain. It is intended to be used with version 3.4.3 of Nethack.

For the purposes of this spoiler, "naked AC" refers to the armor class that your character possesses when he/she is carrying no items, is not polymorphed, and is not under the influence of any protection spell. Intrinsic protection is defined to be the amount by which your character's naked AC is less than 10. Intrinsic protection is usually zero or positive, but it can be negative in the unlikely event that you have eaten a negatively enchanted ring of protection (see below).

In Nethack, a character is considered "protected" if he or she has undergone any discrete event that increases his/her intrinsic protection, even if the amount of the increase happens to be zero or negative as a result of eating a poorly enchanted ring of protection. Being protected affects how much protection you can gain by donating or praying (see below). You can find out whether you are protected by using a wand or potion of enlightenment during your game, or by ending your game and reading the messages that are displayed when your game ends.

Ways to gain intrinsic protection

Here are all the ways to gain intrinsic protection and become protected:

Eat a ring of protection (see Eating Objects spoiler).
- 1/3 chance of effect (message: "Magic spreads through your body as you digest the ring.")
- If the effect occurs, you gain N points of intrinsic protection where N is the enchantment of the ring, and become protected. N is allowed to be zero or negative.
Donate between 400*(XP level) and 600*(XP level) - 1 gold to a priest (see Donating to priests spoiler).
- If you are not already protected, you gain either 2, 3, or 4 points of intrinsic protection (with equal probability of each), and become protected.
- If you are already protected and your naked AC is greater than 1, you gain 1 point of intrinsic protection.
- If you are protected and your naked AC is between 1 and -9, you have a 1/N chance of gaining 1 point of intrinsic protection, where N is your current amount of intrinsic protection.
- If your naked AC is below -9, you do not gain any intrinsic protection.
Pray to your god (see the Praying spoiler and the addendum on praying strategy).
- When your character has sufficiently high luck and alignment and prays successfully on a coaligned altar, a random number from 1 to [(luck+6)/2 rounded up] is selected. If this number equals 6, then you gain one of the following intrinsics (in order of priority): telepathy, speed, stealth, or divine protection.
- In order to gain divine protection by prayer, you must already have intrinsic telepathy, speed, and stealth. If you do, and you are not already protected, then you gain 2, 3, or 4 points of intrinsic protection (with equal probability of each), and become protected. If you are already protected, then you gain 1 point of intrinsic protection, no matter how much intrinsic protection you already have.

Because of program limitations, a character's armor class in Nethack must always lie between the values of -128 and +127. If your AC strays outside of this interval for any reason, it will wrap around to the other side of the interval.

Ways to lose intrinsic protection

The following events will cause your intrinsic protection to be set to zero.

Perform a prayer when it is unsafe to pray.
- See the Praying spoiler for a complete list of the conditions under which praying is unsafe.
Attempt an egregiously offensive sacrifice. Here is a full list of egregiously offensive sacrifices:
- Sacrificing on another god's altar and converting yourself to the altar's alignment.
- Sacrificing a coaligned unicorn.
- Sacrificing any kind of unicorn on that unicorn's altar (see unicorn sacrificing spoiler).
- Sacrificing a former pet.
- (If not chaotic) Sacrificing a member of your own race.
- Sacrificing an identified cheap plastic imitation of the Amulet of Yendor on your own high altar in the Astral plane.
Kill a coaligned priest.
Change alignment by putting on or taking off a helm of opposite alignment.
Have your protection stolen by a gremlin (see Gremlins spoiler).

Unless your protection was stolen by a gremlin, you will still be considered protected after any of these events occur, provided that you were protected before.

David Jao <djao@dominia.org>

Addendum: Prayer and detailed luck strategy spoiler

by Doug Freyburger 02 Mar 2006

For divine protection you want 1d(luck+6)/2 = 6 at the time you pray. Characters start their games with luck=0 on most days, and on full/new moon days it settles back to 0 by turn 600. Before reaching the altar in minetown a character generally knows his/her luck is 0.

The problem with raising your luck via four-leaf clovers is that you need to look up the monster in the table in the prayer spoiler to tell how many luck points you gained. So it's easier to max out your luck at 13 and then move back down to a known number. Below is my commentary on each luck value from 13 down, based on first maxing out your luck and then deliberately moving it to a known value before praying.

13: With maxed out luck=13, 1d(luck+6)/2 is random from 1 to [19/2 rounded up], which can give a result of 10 on down. This gives a 3/10 chance of being crowned and a 7/10 chance of counting down through the rest of the benefits.
12, 11: Gives a result of 9 on down. This gives a 2/9 chance of being crowned, and a 7/9 chance of counting down through the benefits. Luck=11 also gives 9 on down.
10, 9: Gives a result of 8 on down. This gives a 1/8 chance of being crowned, and a 7/8 chance down through the benefits. Luck=9 also gives on 8 on down.
8, 7: Gives 7 on down. The results can be: a) Spellbook, b) AC/protection, c) uncurse all held items (light blue), d) hit points (golden), e) (golden), f) fix and bless weapon, or g) nothing in equal chances. Wonderful for a spell caster! Incidentally, killing a co-aligned unicorn brings your luck five lower. Luck=7 also gives 7 on down. Get there by breaking three mirrors.
6, 5: Luck=6 gives 6 on down. The results can be: a) AC/protection, b) light blue, c) golden, d) golden, e) weapon, and f) nothing in equal chances. Wonderful for a combat wombat! Get there by killing a coaligned unicorn and breaking one mirror. Luck=5 also gives 6 on down. Get there by breaking four mirrors.
4, 3: The results can be: a) light blue, b) golden, c) golden, d) weapon, e) nothing in equal chances. At this point we've dropped off being able to gain protection, but there's still the option of getting a golden glow. The golden glow increases max hit points so it remains a valuable result.
2, 1: The results can be: a) golden, b) golden, c) weapon, d) nothing. Having known positive luck leads to good results when praying.

Given the various treats it makes sense to pick up all available cursed items that you want uncursed, in case the light blue glow happens. It also makes sense to wield any damaged weapon in case the fix-weapon treat happens and lacking any damaged weapon an uncursed one, especially any stack of uncursed missiles like daggers. Over time you'll run out of damaged weapons and slowly build more blessed ones.

Without holding a luckstone, luck maxes at 10 and it would take 2 mirrors to drop your luck down to 6. But without a luckstone your luck drops by 1 every 600 moves, so it would be hard to keep track of your luck.

While holding a blessed or uncursed luckstone, luck maxes at 13 and it would take 4 mirrors to get down to 5-6 for the prayer effect a combat wombat wants, or alternatively 3 mirrors for the spell caster (who wants books as much as AC protection) to get down to 7-8. At this point you could keep the stone in the open, max your luck, break 3 or 4 mirrors, and know you'll never get crowned if you pray every time you reconcile. That could go on until a "create monster" spell no longer makes any monsters on your level if you're a wizard who does not get hungry from casting that spell. My conclusion is that any spell caster who gets "create monster" to 0% failure can use prayer to get an excellent AC with a bit of altar work.

Breaking 3 or 4 mirrors while holding a luckstone has the advantage that it takes you 1 point lower than you need but it still gives the same prayer result when compared to killing coaligned unicorns. On the other hand killing coaligned unicorns may be a goal anyway for an extinctionist player.