The Tetrahedron
The Tetrahedron classically represents Fire, ties to the color of red. Each face is also the alchemical triangle of fire. The Golden Dawn called it the Pyramid of Fire, and used it as the admission badge for the path of Shin. The three upper triangles represents Solar Fire, Volcanic Fire and Astral Fire, while the bottom triangle, often hidden from view is the latent heat. The upper triangles are also linked to the three fire-signs Aries, Saggittaurius and Leo.
