What are a magic item's saves?

Question

We're building a spell that can target magical items, similar to mage's disjunction in Pathfinder. Fifth edition has a spell that targets spells affecting objects: dispel magic, but nothing that directly affects magical items, as far as I can tell. If we want to target magical items, it makes sense to give magical items a save (as in 3.5/Pathfinder).

The easiest way to do this is just to give the item an arbitrary saving throw, with a bonus for rarity. Better still would be giving it a Wisdom or Constitution save.

Borrowing from Pathfinder again (source):

Magical Items: Magic items always get saving throws. A magic item’s Fortitude, Reflex, and Will save bonuses are equal to 2 + half its caster level. An attended magic item either makes saving throws as its owner or uses its own saving throw bonus, whichever is better.

Is there a similar rule in fifth edition? How do you determine a magic item's saves?

Note: I'm not talking about sentient magical items. I'm looking for a rule to apply to regular magical items. Sentient magical items would likely get a bonus though.

Answer 1

No.

RAW:

Only creatures make saving throws. Unattended objects (including magic items) do not make saving throws. But most damaging spells do not affect objects anymore. Almost all of them only affect creatures.

Even the mighty Disintegrate (and it can affect objects) is ineffective on magical objects:

This spell automatically disintegrates a Large or smaller non-magical object or a creation of magical force. If the target is a Huge or larger object or creation of force, this spell disintegrates a 10-foot-cube portion of it. A magic item is unaffected by this spell.

One damaging spell that can affect magical objects is Meteor Swarm:

The spell damages objects in the area and ignites flammable objects that aren’t being worn or carried.

Objects have Armor Class and Hitpoints. Not saving throws. They have a "damage threshold" that works like the old 3.5 hardness.

Magic items have resistance to all damage:

[Comment:] Might be worth pointing out that most magic items do have Resistance to all damage (DMG 141) since that isn't mentioned with the rest of the Object HP rules. – Erik

Homebrewing:

Saving throws are bound to abilities in 5e. If you were to make an item with ability scores, then it would gain saving throws. Animated Objects for example, are treated like creatures when they are animated. They have Ability scores, so they should be able to make saves in these two abilities.

An animated object is a construct with AC, hit points, attacks, Strength, and Dexterity determine by its size. Its Constitution is 10 and its Intelligence and Wisdom are 3, and its Charisma is 1.

(Nobody said they would have great saving throws).

Answer 2

There is no spell or effect in 5e that you could base such an effect on. Dispel magic has no effect on permanent magic items, it only ends spell effects (like magic weapon). Antimagic field disables magical items too, along with all other magic, but does not require a save.

Because of that, objects have no ability scores either, only creatures do:

abilities provide a quick description of every creature's physical and mental characteristics (PHB 173, emphasis mine)

If you wish to create an effect that targets the magic of a permanent magic item, you will have to homebrew it from scratch.