This suit of armour is reinforced with adamantine, one of the hardest substances in existence. While you're wearing it, any critical hit against you becomes a normal hit.
Only creatures and races with a natural armour that could be considered a shell can wear it in it's intended form, otherwise it can be taken apart to gain a set of adamantine plates.
Ignores the rule requiring armour to be removed before sleeping.
This armor consists of a fitted metal chest piece worn with supple leather. Although it leaves the legs and arms relatively unprotected, this armor provides good protection for the wearer's vital organs while leaving the wearer relatively unencumbered.
Notes: Immunity: Critical Hits, Immunity: Bludgeoning, Needs 7 short rest's worth of downtime, with help from someone who has proficiency in smith's tools, and another (or the same person) with proficiency in leatherworker's tools, in order to install the shell-plates onto the wearer's shell., Combat, Warding