crysknife

To create a crysknife in nethack, you first need a worm tooth. A worm tooth can be obtained by killing a long worm. Once the worm tooth has been retrieved from the corpse, a scroll of enchant weapon must be used to enchant the worm tooth to a crysknife. A cursed scroll of enchant weapon will change a crysknife back to a worm tooth.

If the crysknife leaves the inventory of a player or monster (for example, yanked from your hands by a bullwhip), the crysknife will revert back to a worm tooth.

The crysknife is also referred to as "the Death Maker". Before Paul came to Dune, no off worlder had ever seen a crysknife (and lived to tell about it). "Known only by rumor and wild gossip." None were ever allowed to be sold and taken off world. Once drawn, a crysknife could not be returned to its scabbard without drawing blood.

It's possible Frank Herbert's inspiration for the crysknife came from a symbolic wavy dagger found in Bali called the "Kris Knife", which is used in a ritual "Kris Dance".

As every Dune fan knows, knives intended for storage are "fixed". Knives attuned to the owner's electrical field are classified as "unfixed". However, this basic fact seems to have been missed by Dune prequel authors Brian Herbert and Kevin J. Anderson. In their first prequel Dune: House Atreides, the authors describe a fixed crysknife as "keyed to the body of the owner so it would dissolve upon his death". This is of course the exact opposite of the way Frank Herbert describes a fixed knife.

This oversight would not be so bad, if one was writing, say, fan fiction ... or maybe slash. But when Brian Herbert and Kevin J. Anderson come right out and claim their new Dune novels "continue to establish canon in the Dune universe" (emphasis mine) and hint that they're working from detailed notes left by Brian's father, you have to wonder how they could have made such a basic slip up.