Mirror of Smoke was an artifact used by Xolotl in the ancient Mexico to summon a horde of unspeakable horrors to fight with Totec. Totec however found a way to turn the Mirror of Smoke's powers back against Xolotl and trap him inside the artifact. The mirror was hidden away and Totec sacrificed himself to guard over the artifact.
Centuries later Lara Croft discovered the location of Mirror of Smokes, she was however followed by Vasco, who then released Xolotl from it's imprisonment. That also released Totec, who then with the help of Lara Croft trapped Xolotl again in the Mirror of Smoke.