Additional carvings at El Tzompantli depict this Mayan warrior clutching a quiver of arrows and a club tipped with an obsidian (volcanic glass) blade. He is surrounded by images of serpents and flanked by two eagles. Each giant bird is clutching a human heart. Heart extraction was a common form of human sacrifice from 900 – 1524 AD. The eagle was the ruler of the sky and represented authority, control and wisdom.