Azazel

Azazel was a minor character, an Eidolon demon created by Lilith to infiltrate the Resistance. His mission ended in failure when he died at the hands of Umbra.

Biography
Azazel was created by Lilith for the sole purpose of disguising himself as Dieter, who had been captured, and destroy them from the inside out. Unlike other Eidolon demons, Lilith gifted him with the ability to copy the powers and abilities of who he transformed into.

Azazel, disguised as Umbra, approached Dieter alone in the sewers and knocked him out. He delivered Diueter to Lilith and Taylor, then assumed Dieter's form and returned to Etzel's home.

He successfully fooled everyone for a few days, relaying as much information to Lilith as he could (including the existence of Nicholas). However, when Jez, May, Kyle, Nicholas, Umbra, and Veronica emerged into the sunlit street one day, Azazel followed, forgetting he was disguised as a vampire. When he touched the sunlight and did not burst into flames, Veronica assumed he had become a Daylighter. The others saw through his disguise, however, when Azazel imprisoned Umbra in a tomb of rock, and attacked.

Duel with Jez and May, and Veronica and Kyle
Jez and May were the ones who attacked first, and Azazel morphed into Umbra's assuming the Greater Demon's powers. With them, he was able to successfully defeat the Nephilim and Faerie in close combat. However, Veronica and Kyle attacked next, and Azazel had a little bit more difficulty putting them down. Thanks to Umbra's speed and strength, however, he subdued them both, accidentally (but conveniently) mortally wounding Kyle in the process by forcing his splintered ribs into his lung.

Duel with Umbra and death
At this point, Umbra freed himself from his imprisonment, and attacked the overconfident Azazel. The fight was short, and two of them seemed to be at equal levels of strength until Azazel grabbed Umbra and tried absorbing his life force. This plan failed, however, due to Umbra being a Greater Demon and not vulnerable to his own attacks. Umbra flicked Azazel off him, and then repeated the move used on him, but with much greater effect. Umbra drained the demon's life force completely, instead of copying it like he usually did. Azazel, horrified that he had lost, turned into ash and was swept away by the wind, gone forever.