Ring of The Viper (3.5e Equipment)
From D&D Wiki
Ring of The Viper: This ring is garnished with workings of small vipers. Its wearer gains a +5 competence bonus on Bluff checks. Once per minute, the wearer can poison a target with one successful unarmed strike. The target receives 1d10 points of temporary Constitution damage and another 1d10 points of temporary Constitution damage one minute later. Each instance of damage can be negated by a DC 14 Fortitude save. The ability must be declared before the attack and is used for that minute if the attack misses.
Moderate transmutation and necromancy;CL 7; Forge Ring, polymorph, poison; Market Price: 26,950gp