Tephra is a volcanic fragmentary material. More precisely, it is all volcanic products except lava. They are also known as pyroclasts. It forms when magma collides with water, usually glacial water, vitrifying the magma.

A volcanic eruption is, in itself, an explosion of energy. On worlds without magic, it is as simple as opening a valve to release the pressure contained within the world.

On worlds with a more powerful affinity with the arcane, however, the earth's core is often occupied by elementals of fire, and sometimes earth, who can move freely without fear of being extinguished. Sometimes they are even the key to their world's survival, powering the planet's rotation and cycles on its surface. Despite this onerous task, this does not prevent Elementals from being sentient beings with desires, fears and needs. Like other races, they build civilisations. Civilisations that may have differing views on the management of magma and the occupation of the core of their world. This creates conflicts which, for the surface dwellers, result in volcanic eruptions.

This explosion of energy, already incredible, also becomes a source of magic dispersed in volatile fragments known as tephras. By recovering and concentrating these elements, it was possible to create a metamorphosis spell into a fire elemental.

Unfortunately, the process is quite painful: the individual's body is burnt alive, replaced by the energy of the magma and the tephras. Using this alchemical element makes the transformation permanent.