Mousse de Saxe is not a single note, but rather a legendary, complex base accord, renowned for its profound depth and unmistakable 'vintage' character. It presents as a rich, dry, and intensely dark woody-mossy aroma, often intertwined with a pronounced leathery facet that can range from plush suede to rugged, tarry hide. Hints of tobacco, dried leaves, and a subtle, almost licorice-like aniseseed nuance might emerge, alongside an abstract animalic warmth that provides a foundational hum, though rarely overtly fecal. Its texture is often described as velvety yet coarse, like aged parchment or distressed leather, with an underlying dry, almost dusty quality. The intensity is considerable, a powerful presence that anchors a composition. Its evolution is slow and stately, deepening over hours rather than minutes, revealing layers of leathery moss, verdant earth, and a nuanced smokiness. It possesses exceptional projection for a base note, leaving a distinctive sillage, and its longevity is monumental, often clinging to fabric for days. It functions exclusively as a tenacious base note, providing an architectural backbone and an inimitable 'old-world' gravitas.