Fang of Eternal Frostweapon(dagger), very rare

This dagger carved from a fang of Old White Death is still as cold as ice and constantly steams like a breath in the frigid winter air. As a bonus action you can press it against your bare skin, taking 2d8 cold damage, and on the next successful attack with this dagger the target creature must succeed a DC 19 Constitution saving throw. Creatures with resistance to cold damage or that are naturally adapted to cold climates have advantage on this saving throw, and creatures with immunity to cold damage automatically succeed.
On a failed save the target creature is restrained as it begins to freeze solid. A creature restrained by this effect must make another constitution saving throw at the end of each of its turns. If it successfully saves against this effect three times, the effect ends. If it fails three times, it is turned to ice and is petrified. The successes and failures don’t need to be consecutive, keep track of both until the target collects three of a kind. The first time a creature is petrified by this effect the fang becomes mundane and begins to melt.

very rare