Embellished Robes are a variant of Noble Clothes and can be only be found on certain Jarls, such as Jarl Igmund.
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It is impossible to get these via normal means, as they are not found anywhere in the world and the existing sets are worn by essential characters who cannot part with them. If the Dragonborn gets the Noble Clothes, they can get a matching set of robes as Balgruuf the Greater.