Chillblain Armor

Armor (medium or heavy, but not hide), very rare (requires attunement)

This armor is forged from overlapping blue steel plates or blue rings and has a frosted appearance. While wearing this armor, you gain a +1 bonus to AC, and you have resistance to cold damage. In addition, when a creature hits you with a melee weapon attack, it must succeed on a DC 15 Constitution saving throw or become numbed by the supernatural cold radiating from the armor. A creature numbed by the cold can use either an action or bonus action on its turn, not both, and its movement speed is reduced by 10 feet until the end of its next turn.

Curse. This armor is cursed, a fact that is revealed only when an identify spell is cast on the armor or you attune to it. Attuning to the armor curses you until you are targeted by the remove curse spell or similar magic; removing the armor fails to end the curse. While cursed, you have vulnerability to fire damage. If you are hit by a critical hit that deals fire damage while wearing this armor, the armor shatters into useless fragments.