The particular depiction of a sigil is called a "glyph", and this is what practicioners place when using sigils to formulate spells - they place a glyph of a certain sigil, for the sigil itself is the underlying universal. Sigil magic is a prominent part of the Onmyōdō school of magic. Glyphs can essentially be placed with anything that leaves a physic trace upon a surface, although certain substances will greatly increase the efficiacy of the spells, while others decrease it. Each spell and each metaspell has a corresponding sigil; for example, .