Add an artifact crysknife, which is nameable. Add a obj_resists call in the crysknife reversion process to make it so that artifact crysknives either never revert to worm teeth or do so very rarely.

The other properties of such an artifact are unspecified.

Crysknives don’t revert if you’ve killed a monster with it since the last time you picked it up.

When a crysknife leaves your inventory, it starts a timer with 10-50 turns. The timer is canceled if it reenters your inventory. If the timer times out on an unfixed crysknife, it reverts to a worm tooth; if a fixed one times out, it loses one point of enchantment and restarts the timer, or if it’s at +0 it reverts to a worm tooth.

Trying to enchant multiple crysknives at once will fuse them together before trying the enchantment.

If you enchant multiple worm teeth into a single crysknife, the enchantment of the resulting knife is increased by 1 point for each additional tooth involved. This can go up to a maximum of +9, bypassing normal overenchantment dangers.

Fixed crysknives never revert.