Vorpal Blade

This is a very useful weapon. It's an ordinary neutral long sword, but there's a 5% chance of instantaneously killing monsters by beheading. It is shunned by some players because it only does +1 damage and d5 to-hit, but others find the insta-kill to be quite useful.

A Vorpal Blade originally appears in the poem Jabberwocky by Lewis Carroll. In the poem, an unnamed adventurer "took his vorpal sword" in hand and sought the dangerous Jabberwock:

"One, two! One, two! And through and through

The vorpal blade went snicker-snack!

He left it dead, and with its head

He went galumphing back."

The implication is that the vorpal blade beheaded the Jabberwock. Because of the origin of this weapon, in Nethack it has a 100% chance to behead Jabberwocks.

Instakill probability table

The following table summarizes the damage done by the Vorpal Blade. For example, after you hit a monster ten times, there is a 40% change that you have beheaded it. You have also done an average of 55 points of physical damage to it. The odds of beheading a monster rise above 50% after 14 hits, at which point you have damaged the monster for approximately 77 points anyway.

Hits	Cumulated instakill probability	Physical damage to small monsters (avg)
1	5%	2–9 (6)
2	9,75%	4–18 (11)
3	14,26%	6–27 (17)
4	18%	8–36 (22)
5	22.6%	10–45 (28)
10	40%	20–90 (55)
15	53.7%	30–135 (83)
45	90%	90–405 (248)