"Guess who's back from the dead my delectable morsels?"
Lilliana is a strigoi. A creature in ancient Romanian folklore that can shape shift into hideous creatures,invinsibility, speed, and drain life energy out of living creatures.
Centuries ago Lilliana Antonescu discovered Equestria and preyed on everyones Life Energy. Not just for power but for survival too. Ofcourse Princess Celestia banished her for commiting the heinous crime.
Now she's back and badder then ever.
Lillian's personality is a bit negative. She doesn't want to be close to anypony or anything due to painful memories of her past.