|“||Agramon takes the form of whatever most terrifies you. When it is done feeding on your terror, it kills you, presuming you are still alive at that point. Most men — and woman — die of fear before that.||”|
Agramon is a Greater Demon and is also known as the Demon of Fear. Agramon takes the shape of its target's greatest fear and can literally scare beings to death. It lacks its own true physical form, other than its malformed, enormous, hideous shape that seems like a dark cloud of gas with big glowing eyes the size of saucers.
Agramon was summoned by a young warlock named Elias for Valentine Morgenstern in September 2007. Upon being summoned, Agramon managed to break free from the pentagram because Elias' greatest fear was of any demon he summoned on a job escaping its pentagram. Agramon then proceeded to kill Elias, before being put under Valentine's control through the Mortal Cup.
Agramon and Valentine later went to the Silent City to steal the Mortal Sword. Even the Silent Brothers present were not immune to his powers, and all of the Brothers in the Silent City at the time of Agramon and Valentine's attack were ultimately scared to the point of death. Jace, who was being kept in the underground cells, grew scared of the frightful sound the Silent Brothers made and the aura given off by Agramon's presence. Agramon later revealed himself to Jace, though he only knocked him unconscious, likely under Valentine's orders. Aboard Valentine's ship, Agramon showed Jace his greatest fear: a gravely injured Clary seemingly dying in his arms, after which Agramon again knocked Jace unconscious for Valentine.
Agramon later reappeared to Jace, who was wearing the Fearless rune, in the form of Valentine. While Jace had guessed that it was not really Valentine, he was overcome with shock. Jace then stabbed the figure, and Valentine's form appeared to have truly died—momentarily worrying Jace—before the body dissipated into sand and then into thin air.