Before CRISIS ON INFINITE EARTHS, she was a bringer of doom, a wandering spirit living off of one host after another. During World War II, she took possession of the Baroness Paula Von Gunther, a brilliant Nazi saboteur. After the Crisis was over and a single earth was born, Dark Angel/Paula Von Gunther escaped the compression of every Donna Troy into one single person, slipped through the cracks of reality, and once again plagued mankind. During WWII, she became a Nazi occultist and an enemy of Wonder Woman and the Justice Society of America. She also plagued Wonder Woman's mother, Hippolyta, attempting to kidnap Princess Diana but instead capturing Donna Troy. She cursed Donna to live thousands of lifetimes, with each one always ending in tragedy, and each one the life of a former alternate reality Donna Troy. However, Troy fought against her, and eventually she broke the cycle.
And then came INFINITE CRISIS. Dark Angel once again slipped through the cracks, but this time her status was, and remains, unknown. It's possible she is an alternate counterpart of Donna Troy from Earth-7, but she may have a different origin altogether. What is known is that she became a servant of the 52 Monitors who watched over each of the new 52 known universes. She tested Supergirl to see if she deserved to exist in the new multiverse and decided she should be erased from existence. However, the Monitors intervened and assigned her to destroy Earth-48, home of the Forerunners. She was successful in her task. She later pursued Donna Troy, Kyle Rayner, and Jason Todd through the multiverse and found them on Earth-50. She injured several heroes from this world during a battle.
After that, Dark Angel was assigned to Earth-33 and posed as an Oracle of this world of conjurers and mystical denizens. When Viza'aziv, the last remaining Forerunner, arrived and uncovered Dark Angel's plot, Dark Angel shred her disguise and attacked, killing Earth-33's Starman during the melee. She was defeated, but Dark Angel managed to escape before being killed by Forerunner.
Currently, Dark Angel has yet to appear during either the New 52 or DC UNIVERSE REBIRTH, but she's likely still out there, waiting to strike.