|Base item||Unicorn horn|
|Damage vs. small||1d12|
|Damage vs. large||1d12|
|Weapon skill||Unicorn horn|
|Base price||10000 zm|
Like the other two alignment quest artifacts, Nighthorn will never be randomly generated, but is instead found upon killing Nightmare on the single-level Lawful Quest, a portal to which is found between levels 15 and 19. It will only be found if the manner of Nightmare's death would have otherwise left a corpse - disintegrating her or digesting her will not get you Nighthorn. Note that the Key of Law will still be found, though. The dropped Nighthorn will always be cursed and +0, so be very careful before wielding or applying it! Note, that you can't wish for it ("For a moment, you feel something in your hands, but it disappears!").
As a unicorn horn
To neutrals or chaotics, this is likely to be very nearly useless. It provides no benefit from being carried, and the 8d6 blasting damage it will inflict one-fourth of the time it is used makes it difficult, if not impossible, to use as a unicorn horn.
For lawful characters it isn't much better. At least normal unicorn horns aren't cursed when dropped. Since it isn't intelligent, it doesn't resist curses either. And at that point, a lawful character probably already has a blessed and enchanted unicorn horn. The only advantage of nighthorn is the "cool" factor.
As a weapon
A mid-game character might find this a useful weapon, as reflection becomes a larger and larger priority as the game goes on. Lawfuls in particular might benefit from having it function as both a unicorn horn and a weapon, since enchanting helps both of these functions. However, even a neutral or chaotic who really needs reflection and is not restricted in the unicorn horn skill might find it handy. Unfortunately, Nighthorn simply does not do enough damage to be a contender in SLASH'EM's later game. It is also two-handed; while it does provide the same property that a shield of reflection provides, it does not provide the same 6 or 7 AC bonus of a well-enchanted shield.
Nighthorn is also implemented in dNethack as an chaotic intelligent unicorn horn, where it is much more valuable. Nighthorn is dropped from Nightmare, but she now appears in the beginning of the Chaos Quest (somewhere at the Earth Temple). As her and the horn are also chaotic now, and thus will be peaceful to any chaotics, a chaotic who wants the horn may need to take the -5 luck/alignment penalty for killing a coaligned unicorn. It will also always blast its user when picked up, and blast and evade the grasp of lawfuls.
Nighthorn grants +1d12 to-hit and +1d24 fire, causes a fiery explosion on hit, and grants fire resistance while wielded. It also counts as a luckstone and (if you are chaotic only) duplicates the effects of a scroll of scare monster when dropped on the ground. This will only fend off non-chaotic monsters though. It can be #invoked for levitation. It is always generated cursed.
As unicorns are now one-handed in dNethack, it can be a viable weapon, save the fire resistance of many demons. It depends on the player's situation.
No entry. The parser recognizes "horn" in "nighthorn", and gives back the entry for "horn"( The song of Roland ).