Skill

NetHack's skill system allows different roles to attain different proficiencies in the use of different weapons and spells. Skills can be advanced using the #enhance command. When you become able to advance a skill, you will see the message "You feel more confident in your (weapon/fighting/spell casting) skills." Otherwise, if you have multiple skills that can be advanced, you will get the message "You feel you could be more dangerous!" Skills are not advanced automatically because advancing them requires free skill slots which can only be gained by levelling up.

Training skills

Introduction

Most skills in NetHack have four possible levels: Unskilled, Basic, Skilled and Expert. Martial arts has two levels beyond expert: Master and Grand Master. Generally speaking, characters start at basic skill with the weapons and spells with which they begin their adventure and unskilled in all others.

Use the #enhance command at any time to get a list of skills which you can train. If a skill does not appear on this list, your role is said to be restricted in this skill, meaning that no amount of training will enable it to advance beyond unskilled. (If you receive an artifact weapon from your god, you will be "unrestricted" in this weapon if necessary, and will be able to advance it to Basic.) #enhance will also indicate which of the listed skills have been trained up to their maximum levels. Tables of maximum skill levels can be found in Dylan O'Donnell's spoilers weap-343.txt and spl1-343.txt.

As a general rule, skills are trained by using them successfully. There is a trick to training spell skills: practise with a low-level spell in the school you want to train until your skill improves enough that you can cast high-level spells in that school. For example, train up divination spells by casting light so that you can cast magic mapping and identify more reliably.

Technical details

To advance a skill, you need to have enough free skill slots and to have practiced it enough. You begin the game with no free skill slots and gain one each time you gain an experience level. It costs one skill slot to advance a weapon skill from Unskilled to Basic, two to go from Basic to Skilled, and three to go from Skilled to Expert. Other skills take one skill slot to go from Unskilled to Basic, one to go from Basic to Skilled, two to go from Skilled to Expert, two to go from Expert to Master and three to go from Master to Grand Master. If you lose an experience level, you will also lose a skill slot, which may result in losing your most recently earned skill.

The table below shows the total number of successful uses of a skill required to reach each level. If you start with a skill at Basic, you are also precredited with 20 successful uses of that skill.

Skill Level	Successful Uses
Unskilled	0
Basic	20
Skilled	80
Expert	180
Master	320
Grand Master	500

Hitting a monster for more than one point of damage (including from a distance) counts as a successful use of a weapon skill, bare-handed combat or martial arts. Riding continuously for 100 turns counts as a successful use of the riding skill. Successfully casting a level n spell counts as n successful uses of the relevant spell casting skill.

Effects of skills

Improving weapon skills can improve your to-hit or damage bonuses. Improving spellcasting skills improves your chances of casting spells in that school successfully. Certain spells also have better effects when cast at skilled or expert level. Cone of cold and fireball create explosions rather than a ray; remove curse acts like a blessed scroll; levitation acts like a blessed potion of levitation (you can descend at will); jumping can go further; protection takes longer to decay; detect monsters and confuse monster will continue to stay in effect for longer.

Bare hands combat and martial arts skills are an exception to this rule: they never grant a to-hit bonus, and their damage bonus applies only to 50% and 75% (respectively) of all hits.

Quoting from Kate Nepveu's spoilers at http://www.steelypips.org/nethack/343/weap-343.html :

Skill levels and bonuses, part 1

Skill Levels and their Bonuses

	Needed		Weapon		Two-Weapon
Skill Level	Hits	Exp	+Hit	+Dam	+Hit	+Dam
Unskilled	0	0	-4	-2	-9	-3
Basic	20	1	0	0	-7	-1
Skilled	80	2	2	1	-5	0
Expert	180	3	3	2	-3	1

Weapon skills and bonuses, part 2

Weapon Skills and their Bonuses

	Needed		Riding		Bare-hand	Martial
Skill Level	Hits	Exp	+Hit	+Dam	+Dam	+Dam
Unskilled	0	0	-2	0	0	+1
Basic	20	1	-1	0	+1	+3
Skilled	80	1	0	+1	+1	+4
Expert	180	2	0	+2	+2	+6
Master	320	2	-	-	+2	+7
Grand Master	500	3	-	-	+3	+9

Skill tables

Key
-	Restricted
b	Basic
S	Skilled
E	Expert
M	Master
GM	Grand Master

Weapon skills

Role Skill	Arc	Bar	Cav	Hea	Kni	Mon	Pri	Rog	Ran	Sam	Tou	Val	Wiz
dagger	b	b	b	S	b	-	-	E	E	b	E	E	E
knife	b	-	S	E	b	-	-	E	S	S	S	-	S
axe	-	E	S	-	S	-	-	-	S	-	b	E	S
pick-axe	E	S	b	-	b	-	-	-	b	-	b	S	-
short sword	b	E	-	S	S	-	-	E	b	E	E	S	b
broadsword	-	S	-	-	S	-	-	S	-	S	b	S	-
long sword	-	S	-	-	E	-	-	S	-	E	b	E	-
two-handed sword	-	E	-	-	S	-	-	b	-	E	b	E	-
scimitar	S	S	-	b	b	-	-	S	-	b	S	b	-
saber	E	b	-	b	S	-	-	S	-	b	S	b	-
club	S	S	E	S	b	-	E	S	-	-	-	-	S
mace	-	S	E	b	S	-	E	S	-	-	b	-	b
morning star	-	S	b	-	S	-	E	b	b	-	b	-	-
flail	-	b	S	-	b	-	E	b	S	S	b	-	-
Role Skill	Arc	Bar	Cav	Hea	Kni	Mon	Pri	Rog	Ran	Sam	Tou	Val	Wiz
hammer	-	E	S	-	b	-	E	b	b	-	b	E	-
quarterstaff	S	b	E	E	-	b	E	-	b	b	b	b	E
polearms	-	-	S	b	S	-	S	b	S	S	b	S	S
spear	-	S	E	b	S	b	S	b	E	S	b	S	b
trident	-	S	S	b	b	-	S	-	b	-	b	b	b
lance	-	-	-	-	E	-	b	-	-	S	b	S	-
bow	-	b	S	-	b	-	b	-	E	E	b	-	-
sling	S	-	E	S	-	-	b	-	E	-	b	b	S
crossbow	-	-	-	-	S	b	b	E	E	-	b	-	-
dart	b	-	-	E	-	-	b	E	E	-	E	-	E
shuriken	-	-	-	S	-	b	b	S	S	E	b	-	b
boomerang	E	-	E	-	-	-	b	-	E	-	b	-	-
whip	E	-	-	-	-	-	-	-	b	-	b	-	-
unicorn horn	S	-	b	E	-	-	S	-	-	-	S	-	-

Other combat skills

Role Skill	Arc	Bar	Cav	Hea	Kni	Mon	Pri	Rog	Ran	Sam	Tou	Val	Wiz
bare hands	E	M	M	b	E	-	b	E	b	-	S	E	b
two weapon combat	b	b	-	-	S	-	-	E	-	E	S	S	-
riding	b	b	-	-	E	-	-	b	b	S	b	S	b
martial arts	-	-	-	-	-	GM	-	-	-	M	-	-	-

Spell skills

Role Skill	Arc	Bar	Cav	Hea	Kni	Mon	Pri	Rog	Ran	Sam	Tou	Val	Wiz
attack	b	b	b	-	S	b	-	-	-	b	-	b	E
healing	b	-	-	E	S	E	E	-	b	-	-	-	S
divination	E	-	-	-	-	b	E	S	E	b	b	-	E
enchantment	-	-	-	-	-	b	-	-	-	-	b	-	S
clerical	-	-	-	-	S	S	E	-	-	S	-	-	S
escape	-	b	-	-	-	S	-	S	b	-	S	b	E
matter	b	-	S	-	-	b	-	S	-	-	-	-	E

UnNetHack

UnNetHack changes the number of successful uses of a skill required to reach each level. As of UnNetHack 3.6.0, the new values are:

Skill Level	Successful Uses
Unskilled	0
Basic	100
Skilled	200
Expert	400
Master	800
Grand Master	1600