Zenir's Spiked Armour

Armour - Uncommon Half plate - Medium - AC = 15 + Dex modifier (max 2) - Disadvantage on Stealth checks
This suit of non-magical armour is studded with bone and iron, forming spikes and blades which jut out from the body in several crucial places.
An adjacent creature that grapples the wearer or is grappled by them takes 2d4 piercing damage. A creature takes 2d4 piercing damage if it starts its turn grappling or being grappled by the wearer.