Source: Dungeons and Dragons - Honor Among Thieves.

Wondrous Item, legendary (requires attunement by a Sorcerer, Warlock, or Wizard)

The wizard Mordenkainen crafted this sleek, golden helmet. If he created other helms of disjunction, they have yet to be found.

As an action while wearing this helm, you can use it to emit an antimagic pulse in a 300-foot-radius sphere centered on yourself. The pulse has the following effects:

Magic Item Disjunction. Potions and scrolls in the area are destroyed. All other magic items in the area have their magical properties suppressed for 1 minute. Artifacts are unaffected by this property, as are magic items on your person.

Spell Disjunction. Any ongoing spell ends if the creature, object, or area affected by it is even partly in the pulse’s area.

Wave of Force. The antimagic pulse is strong enough to knock down creatures close to you. Each creature within 30 feet of you must succeed on a DC 15 Strength saving throw or have the prone condition.

Once you use the helm’s property, it can’t be used again until 1d4 days have passed.