Ambergris

Ambergris is a waxy secretion produced in the digestive tract of sperm whales, ejected into the ocean and aged by sun and salt for years. Natural ambergris is rare, expensive, and ethically fraught (it's only collected after beaching, but whale populations are protected). It smells of marine, tobacco-like, slightly fecal warmth with a 'sweet ocean' character that's unlike anything else. Synthetic ambergris (ambroxan, ambroxide, cetalox) is now the universal substitute. Natural ambergris tincture appears in a handful of ultra-luxury compositions; everything else uses the synthetics.