Zorbos (from Tomb of Annihilation, p. 41) have the following Destructive Claws attack (emphasis mine):
Melee Weapon Attack: +3 to hit, reach 5 ft., one target. Hit: 8 (2d6+1) slashing damage, and if the target is a creature wearing armor, carrying a shield, or in possession of a magic item that improves its AC, it must make a DC 11 Dexterity saving throw. On a failed save, one such item worn or carried by the creature (the targets choice), magically deteriorates, taking a permanent and cumulative -1 penalty to the AC it offers, and the zorbo gains a +1 bonus to AC until the start of its next turn. Armor reduced to an AC of 10 or a shield or magic item that drops to a 0 AC increase is destroyed.
Is it possible to repair a magical piece of equipment (+X armor, +X shield, ring of protection, etc.) that has been damaged by the zorbo's Destructive Claws attack?
Best Answer
So like many special abilities in supplemental adventures we need to consider the intent. I believe that based on the wording of the Zorbo's ability ("permanent") that the intent is that this is a magical deterioration that cannot be simply mended with the cantrip or through other simple means.
However, this is ultimately up to the dungeon master running the campaign. It is entirely possible that higher level magic could repair this damage.
Advice: If you are the DM, I would suggest asking yourself the question "what makes the more interesting story?". Is it more important that your world has consequences that cannot be undone and cement that it is a dangerous place? Or is it more important to motivate your players on quests they want to go down? If I was a DM I would find out what was important to the players and chase the fun of the scenario. Maybe they need to go and find a fabled blacksmith wizard who can undo the damage done? Or potentially find a material that can be used by a character to remove the magical damage that is preventing the item from being reforged?