825.2. Unique is not functionally short for any rules text, and instead provides a restriction to players during Deck Construction.
825.2.a. A Deck can contain only one card of a given name if the card has Unique
825.2.b. If a card is a Signature card and is also Unique, then that Deck can contain any combination of three Signature cards, but still only one of each named Unique card.