Beaten Frostrim (5e Equipment)
From D&D Wiki
Weapon (broken sword), very rare (requires attunement)
A deep blue sapphire is nestled in a gleaming silver pommel. A slender blade shoots from the golden-outlined cross-guard broken in half, the breaking-point looking like shattered glass. The edge is cold to the touch and a faint, thin mist surrounds it at all times. This magic weapon does not apply to the normal "10% chance of breaking completely on a hit" feature that a broken sword has.
You gain a +2 bonus to attack and damage rolls made with this weapon. Any creature hit with this weapon must make a DC 14 Constitution saving throw at the end of their turn or take an additional 2d6 cold damage or half as much on a successful one.