The Fourth Cause
Klara is a revenant with unclear association at this point; she previously served Christoph however she says the relationship was not a willing one, and she is seeking succor with another denizen of Seattle now.
Klara possesses the abilities of a revenant, one that is born of breeding of ghouls for generations, and they possess several lessened abilities of vampires. She does age, however more slowly than humans, and therefore her age is questionable. She can learn the abilities of vampires, however the blood her body produces is weak in comparison and abilities lesser. She seems to have some ability with intuition and precognition, and is able to read the auras of other beings to discern what they are as well as their current emotional state.
She has said that she is hardier than the average human and more resistant to damage. She also can manifest strength greater than what her frame would be apparent of, and can briefly call upon bursts of preternatural speed. more importantly, she is able to issue simple commands to beings that must be obeyed, and can implant or wipe memories and commands from the mind of others. She is also trained as a lawyer and likely has practiced successfully for several years.
Beyond the fact that Klara was forced to serve Christoph until his recent death, nothing is known of her history.
Since the explosion at Kindred Hospital, it appears Klara has been staying with Anna Vienus.