T.a. Miles said this quote

“ His angelic wings blackened when the dark fury assailed his mind. Summoning new strength from the unholy power that ravaged his soul, grieved to drastic levels of desperation by the tainting of the holy light within him, he combated ally and enemy alike, bent on destroying both sides in order to ensure the quelling of the dark energies there and then. For days and nights, the lone warrior bathed himself in the blood of angels and demons. And when it was over, he stood alone on contaminated land, with a contaminated soul. He was banned forever from Heaven and not even Hell had space for a creature which seemed to cherish Oblivion over Pandemonium. The dark angel, not so far removed from his former self as his superiors seemed to believe, died on the edge of the cliffs, of utter loneliness and despair. ”