A physical manifestation of your Pact to the Lord of Shadow's a thick black shadow seeps from a brand on your shoulder turning into a hardened black armor that flexes with the body offering some measure of protection while mainly relying on the host's own dexterity.
While wearing this Armor you gain advantage on Stealth checks.
In complete darkness you can use your action to become invisible. This lasts until you attack, cast a spell or move.
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: Advantage: Stealth, Proficiency: Breastplate