A crysknife is a weapon that can only be produced by enchanting a worm tooth. It has a +3 to-hit bonus and does d10 damage against both small and large monsters, making it a nice choice for #twoweaponing. However, if it leaves your possession, it reverts back into a worm tooth (when fixed, this only happens 10% of the time). It can safely be put in a container without reverting, as long as that container remains in your possession. Crysknives count as throwing weapons, so they get a to-hit bonus when thrown. Because of their reversion property, throwing them is typically not a good idea.