Ariane (Earth-43)

Ariane (Earth-43) was a researcher in the occult and an ally and advisor of Batman as he explored the supernatural and his transformation into a vampire.

History
It is unknown when Batman and Ariane met previously, but they were at least professionally acquainted with each other before the red rain and the throat-slash victims began; most likely Batman consulted her expertise on an old case.

Red Rain
When Batman began to suspect that recent murders involving the victims having their throats slashed and his own strange dreams may have a supernatural connection, he went to visit Ariane to talk with her about vampire lore. Aware of Batman's scientific background, Ariane talked about vampires by reasoning that the transformation could be triggered by venom in the fangs that transformed the bitten subject. She was intrigued at Batman's speculation about the possibility of vegetarian vampires who would not feed on humans, but acknowledged his argument that vampires could be considered evil due to them having once been human and therefore having a choice at whether or not to feed. Her insight into vampires' powers proved useful to Batman as he investigated the murders and learned more about what was happening to him, culminating in his own transformation into a vampire to oppose Dracula.

Bloodstorm
Some time later, Batman visited Ariane once more to talk with her about the existence of were-creatures following his encounter with the Cat-Woman. Again keeping his scientific background in mind, Ariane speculated that the moon's influence on the transformation could be caused by it creating 'tides' in the water within the human body. With that information confirming his encounter with Selina, the now-vampiric Batman asked if there was any way for a vampire to resist the lure of blood. Although she knew that it would anger him, Ariane informed him that, while there were myths that the selfless love of a woman could ease the compulsion, ultimately vampires would always drink and succumb to their strongest urge.

Crimson Mist
As he increasingly succumbed to his vampire instincts, Batman, seeking some means of escape from the torment of evil and insanity his unlife had become, contacted Ariane once more. Although he confirmed that he had become as evil as he looked, he assured Ariane that her life was only in danger if it tempted him long enough, as he had fed well and required information from her more than blood. However, Ariane was unable to tell him if a vampire could ever truly die, as Batman had already confirmed that stakes merely immobilised rather than killed and Ariane was unable to tell him if a vampire would retain consciousness when disintegrated into dust. His temper shortened by his own insanity and self-loathing, Batman swept her books aside and leapt from her window, angrily proclaiming that Ariane was nothing but a useless bag of blood.

Note
Ariane is the only character in the Batman- Vampire trilogy to survive all three novels.