Leather Golem Armor

From Lost Laboratory of Kwalish, page 55.

Description
Armor (leather armor), rare (requires attunement).

Strange rituals have repurposed the body of a flesh golem into this partially sentient suit of leather armor. While wearing this armor, you gain a +1 bonus to AC and to saving throws against spells and other magical effects. In addition, you gain the following properties:

Immutable Form. You are immune to any spell or effect that would alter your form.

Lightning Absorption. You gain resistance to lightning damage. Whenever you take lightning damage, you gain 5 temporary hit points.

Curse. This armor is cursed, and becoming attuned to it extends the curse to you. Until the curse is broken with a Remove Curse spell or similar magic, you are unwilling to part with the armor. In addition, while you wear the cursed armor, you gain the following properties:
 * Aversion of Fire. If you take fire damage, you have disadvantage on attack rolls and ability checks until the end of your next turn.
 * Berserk. Whenever a critical hit is made against you, roll a d6. On a 6, the armor causes you to go berserk. On each of your turns while berserk, you attack the nearest creature you can see. If no creature is near enough to move to and attack, you attack an object, with preference for an object smaller than yourself. Once the armor causes you to go berserk, it cannot be removed. You continue to attack until you are incapacitated or until another creature is able to calm you with appropriate magic (such as a Calm Emotions spell) or a successful DC 15 Charisma (Persuasion) check.