Plate Armour of Etherealness

Armour (plate) (requires attunement)

Rarity: Legendary

While you’re wearing this armour, you can speak its command word as an action to gain the effect of the etherealness spell, which last for 10 minutes or until you remove the armour or use an action to speak the command word again. This property of the armour can’t be used again until the next dawn.

Source: Player’s Handbook