SRD:Sword of Life Stealing

Sword of Life Stealing: This black iron +2 longsword bestows a negative level when it deals a critical hit. The sword wielder gains 1d6 temporary hit points each time a negative level is bestowed on another. These temporary hit points last for 24 hours. One day after being struck, subjects must make a DC 16 Fortitude save for each negative level or lose a character level.

Strong necromancy; CL 17th; Craft Magical Arms and Armor, enervation; Price 25,715 gp; Cost 12,857 gp and 5 sp + 1,029 XP.