Black oud is a rare and highly prized form of agarwood from the Aquilaria tree. It has a deep, dark color and a rich, resinous fragrance with smoky, woody, and earthy notes. Known for its intense, long-lasting aroma, black oud is used in luxury perfumes, incense, and spiritual rituals. Due to its rarity and high resin content, it is one of the most expensive types of oud.