Katana

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Name	katana
Appearance	samurai sword
Damage vs. small	1d10
Damage vs. large	1d12
To-hit bonus	+1
Weapon skill	long sword
Size	one-handed
Base price	80 zm (+10/positive enchant)
Weight	40
Material	iron

A katana is a one-handed weapon that deals d10 damage to small monsters and d12 to large monsters, with a +1 bonus to hit. When unidentified, it appears as a samurai sword; Samurai start with one. The sole artifact katana is Snickersnee.

The only differences between a katana and a long sword are the +1 bonus to hit, the katana's d10 damage to small monsters (as opposed to d8 for a long sword), and the fact that a katana cannot be converted into Excalibur by dipping in a fountain (attempting to do so will only rust the katana). Because a katana is the most damaging non-artifact weapon to use the long sword weapon skill, it is often a desirable off-hand weapon for two-weapon combat.

Generation

Katanas are very rare; only 4 in 1000 (0.4%) of all randomly spawned weapons will be katanas, making them the seventh-rarest weapon in the game (tied with lances, among others). This makes getting one for most classes largely dependent on random chance.

As noted above, Samurai start with one in their initial inventory, and a Samurai hoping to twoweapon should generally keep their original, as they're quite rare; should anything happen to it, it's possible to get another during the Samurai quest. Bones from a Samurai are another chancy way to get a katana. While a samurai player monster has a 50% chance of getting a katana, they're only normally generated in the Samurai quest or on the Astral Plane. Reverse genocide never spawns monsters with items, so trying it would waste the genocide scroll.

One good place to look is the Castle stores—collectively, there is a decent 5.46% chance of finding one there. Death drops are another small chance of getting a katana—in Gehennom, where weapons are spawned with about 20% of all items, there is about a 0.0136% chance that a given monster will have a katana in their inventory. At such minuscule odds, however, one must slay 2115 creatures to attain just 25% confidence of getting one.

Randomly spawned shops are another—though by the time the player is worrying about acquiring one, they've likely gone through all the stores that the Dungeons of Doom have to offer. Late in the game, Orcus-town in particular has a small chance of having a katana spawned. The two general stores have a collective 3.15% chance of having a katana, assuming there are no mimics.

If the game has a portal to Fort Ludios, each soldier has a guaranteed weapon, as well as the usual death drops. The 87 Yendorian army members there have roughly a 0.59% chance of spawning a katana to plunder through death drops alone. However, the large number of weapons otherwise spawned may make it possible to polypile for the katana. To be 50% confident to attain a katana, one need polymorph 173 items—easily doable with the 87 weapons assured to be there.

The table below relates the chance of getting a katana, assuming all the weapons are placed onto one pile, are uncursed, and the player has maximized their luck, so as to lessen the chance of hostile iron golems. The confidence given is overall, or cumulative; if the player does not get it the first time, the odds do not increase.

Charges	0	1	2	3	4	5	6	7	8
Confidence	00.00%	23.01%	36.72%	45.38%	51.09%	54.97%	57.68%	59.6%	60.99%
Polyfodder left (avg)	87	65.25	48.94	36.70	27.53	20.65	15.48	11.61	8.71
Total items polymorphed	00.00%	66.25	114.19	150.89	178.42	199.06	214.55	226.16	234.87

Origin

Despite being better than ordinary long swords in NetHack, historically speaking, katanas were no better than an equivalent European sword. In the same era, while many katanas were better than European broadswords, this was simply because katanas were not mass produced (recall that Europe was often at war, and Japan quite isolated); in fact, owing to poorer quality steel in Japan, in a fairer comparison (non-mass-produced European sword) katanas were actually worse. The fact that NetHack's katanas are better than long swords likely stems from Dungeons & Dragons.

Due to the large number of soldiers in the game, the long swords in NetHack are most likely mass-produced. Furthermore, the +1 to-hit may be a nod to D&D, in that that is the same bonus given to masterwork equipment. However, this still does not account for the fact that the stereotypically better elven equipment, the elven broadsword, is still worse (on average) than a katana.

Average damage calculation

The average damage calculations in the following table do not include bonuses from weapon skills, strength, or from using a blessed weapon against undead or demons.

Weapon	Small monsters	Large monsters
+0 katana	$\frac{1+10}{2}=\bold{5.5}$	$\frac{1+12}{2}=\bold{6.5}$
+7 katana	$\frac{1+10}{2}+7=\bold{12.5}$	$\frac{1+12}{2}+7=\bold{13.5}$

Encyclopedia entry

The katana is a long, single-edged samurai sword with a
slightly curved blade. Its long handle is designed to allow
it to be wielded with either one or two hands.