The disintegrator is a type of monster added in the Biodiversity patch. Its attack chooses a random worn or wielded piece of equipment to disintegrate, including your main weapon; cloaks, body armor and shirts count as one possibility for this purpose. The selected item has a chance of 5% to resist the disintegration (50% for artifact weapons; 100% for invocation artifacts and your quest artifact). If this selects a body part that is not covered by armor, you are disintegrated. Disintegration resistance prevents this attack from disintegrating anything.
Disintegrators also have the passive ability to disintegrate objects they are hit with, including gloves (but not rings) if fighting without a wielded object; as with the active attack, ordinary objects have a 5% chance of resisting while artifacts have a 50% chance. Disintegration resistance does not prevent this from happening. However, if you hit a disintegrator without gloves or a weapon and are not disintegration resistant, you disintegrate. Currently, stethoscopes applied to disintegrators do not disintegrate.
Similar to cockatrices, disintegrators have an instant death attack which is triggered by touching the monster; this means that you can die by trying to help a disintegrator out of a pit or be disintegrated by trying to saddle a disintegrator (the latter might also cause your saddle to be disintegrated). However, since they never leave corpses, you cannot die by trying to tin one.
As of the latest development version of UnNetHack, disintegrators are no longer generated and are not valid polymorph forms. Having them appear randomly was deemed too cruel even for (Un)NetHack. They are genocidable, so can be created by reverse genocide, wishing for a figurine, or animating a statue.
The disintegrator appears in Slash'EM Extended too, where it is a lot less dangerous due to the lack of passive disintegration effects. In that variant, their main danger is the melee disintegration attack and the fact that disintegrators can randomly spawn everywhere.
It is true origin story of this monster - see this rgrn thread.
>>when you *dream about* the game
>>Not just the "Hey, I'm in Nethack!" dream (haven't we *all*
>>had that one?) but the "sitting at the computer playing" dream.
>>All of a sudden, a bright green R approached. "Bright green?"
>>thought I. And I threw a couple darts at it:
>> The blessed rustproof +4 dart hits the disintegrator!
>> The blessed rustproof +4 dart disintegrates!
>> The disintegrator hits! Your cloak crumbles and turns to dust!
>> The disintegrator hits! Your armor turns to dust and
>> falls to the floor!
>>Engrave the E-word?
>> Wield what? b - the blessed +2 Magicbane
>> The disintegrator hits! The blessed +2 Magicbane dissolves!
>> The disintegrator hits! You fall apart!
>>Then I woke up and thanked Thoth there's no such thing as
>I smell a sadistic YANI. DON'T GIVE THE D*VT**M IDEAS!!!!
Too late. It is killable, though. At least in wizard mode.
by kcolrawyksthgin, g33kd00d and Nicholas Aodhagan Webb]