Ethereal Shield

Prerequisite: 12th Level, Pact of the Bastion feature
As an action, you may form a hemispherical dome with a radius of up to 10 feet. This dome is utterly impenetrable, confers total cover and blocks line of sight - you cannot hear or see anything outside the dome while inside it and vice versa. This dome lasts until the beginning of your next turn. You can't use this ability again until you finish a short or long rest.