Mizzium Armor

This suit of armor is reinforced with a magically
enhanced metal alloy called mizzium, which is
made in Izzet foundries.
While you're wearing the armor, any critical hit
against you becomes a normal hit. In addition,
when you are subjected to a magical effect that
allows you to make a STR or CON saving throw
to take only half damage, you instead take no
damage if you succeed on the saving throw.