Ringed Knight Armor (5e Equipment)
From D&D Wiki
Armor (half plate), very rare (requires attunement)
The malformed, misshapen armor of the Ringed Knights: the first early men whose armor was forged in the darkness of the Abyss, betraying a smidgen of life.
This magical, half plate armor weighs 38 lbs. and gives its attuned wearer an additional +1 bonus to their AC. While attuned to this branded armor, you have resistance to fire and necrotic damage but are prone to dream of the cold, dark comfort of the Abyss.
After this ability has been used 3 times, roll a d20. If you roll below your level, you gain a personality trait from the indefinite madness table. If this happens more than three times, your character goes Hollow, attacking any living being near it until it has been put down for good. However, should you roll above your level, you remain in a perfectly healthy mental condition… for now.