Bristleback Hide (Patreon)

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

A spiny set of armor fashioned from the hide of a massive plant-like creature that roams the Gilded Frontier. This item can hold 3 charges and loses all charges if they are not expended within 1 minute of gaining a charge. The first time each turn you are hit with a melee attack by a creature within 5 feet of you, that creature takes 1d8 piercing damage.

Thorny Retaliation. Each time you are hit with a melee attack while this item is thorned, this item gains 1 charge, storing the force of the attack. If it were to gain a charge when it cannot hold any more charges, its thorns explode outward expending all stored charges. Each other creature within 15 feet of you must make a DC 15 Dexterity saving throw, taking 3d8 piercing damage on a failure or half as much on a success. Once the thorns have exploded outward, this item is no longer thorned. The thorns regrow after you finish a short or long rest.

Syphoning Cestus. The off-hand of this armor is large and bulky, built from a bristleback’s massive stinger. You cannot wield a shield in this hand, but you can use features that normally require a shield while wearing this armor. 

Additionally, you can make attacks using the stinger of this armor, which counts as a simple melee weapon that deals 1d8 piercing damage on a hit. While this armor is not thorned, you can cause a creature hit by this attack to make a DC 16 Constitution saving throw. On a failure this armor immediately becomes thorned and the creature takes an additional 1d8 necrotic damage and becomes parched. Constructs, Undead, and creatures that are already parched are immune to this effect. Plants and creatures made primarily from water have disadvantage on the save and take double the necrotic damage.

A parched creature immediately gains 1 level of exhaustion, then gains 1 more level each hour that passes. Once a creature consumes 1 day’s worth of water, it is no longer parched and loses all levels of exhaustion gained from being parched.

Of all the dangers across the Gilded Frontier, there are few as insidious and ferocious as the Bristleback. A goliath chimera of plant, lizard, and scorpion, it hides amongst other large cacti before ambushing its prey. Even if one avoids its piercing tail that saps the moisture from its target, they will undoubtedly fall victim to its piercing hide. Those adventurers who have slain such a formidable foe make use of its natural defenses, creating armor that retaliates with the creature’s exploding spines.