What happens if you obtain a cursed item while already attuned to your maximum number of attuned items (three)?

Question

Reference: daze413's answer to "As a monk, can I use Deflect Missiles to protect my ally?"

Scenario: Monk already has his three attuned magic items. Monk picks up a shield of missile attraction, which is a cursed item, and uses it for awhile. This should cause him to pick up the curse. Monk discards the shield of missile attraction.

If I read correctly, most magic items do not function unless attuned, and using a cursed item causes the attunement to pick up automatically (otherwise what's the point)?

But now we're trying to exceed the attunement limit by using a cursed item. Oops. Contradiction. Now what?

Answer 1

The Shield of Missile Attraction does not automatically attune to characters who use it. Attuning to it causes its "curse" to kick in, but it has no ability to automatically attune or force its wielder to attune. The point you might be missing is that unless you attune to it, you also don't get the resistance to ranged weapon attacks.

Certain magic items require a user to attune to them before their magical properties can be used.

The resistance to ranged weapon attacks is a magical property, and the Shield of Missile Attraction includes the "(requires attunement)" tag, so you don't get the "curse" or the benefit unless you attune.

You may have noticed that I put scare quotes around "curse". Yeah, that's an important point here. The shield grants you resistance to all ranged weapon attacks, so causing them to hit you instead of your allies isn't really a curse - it's the greatest benefit the shield has to offer.