Throughout Mesoamerica, from c. 1500 BC to the Spanish conquest and beyond, obsidian was centrally located in the physical and symbolic worlds of indigenous societies. The aesthetic engagement with obsidian, based on its unique physical properties in a world without metal tools, bestowed distinctive kinds of agency on artefacts made from this dark volcanic glass—especially as blades used for bloodletting and human sacrifice. Linked to landscape, cosmology and myth, obsidian attained its apotheosis as the Aztec deity Tezcatlipoca, 'Lord of the Smoking (Obsidian) Mirror'. After the conquest, its symbolic role was re-aligned. Used to decorate early Christian atrial crosses, it was viewed as adornment by Catholic priests, but as a syncretic continuation of pre-Columbian belief by native peoples.