Cornelius Corby, Corbue or Corvey, AKA Corvinus Corax
A research witch. Despised by Sanderon Magnus for his affected sinisterness, he nonetheless worked together with Sanderon, Bess Johnswort and young Atra to realise their dream of learning to shapeshift. The dream became a nightmare for him after the dying Bess put a curse on him and his descendents, who became known as the Corbies.
"Corvinus Corax" is of course an assumed name. Like many wizards, philosophers, alchemists and scientists working in the middle ages, Cornelius Corvey took advantage of the custom of latinizing one's name to change it into something cooler. Cornelius liked black, goatees and long capes and was fascinated by flight, so the name Corvinus Corax suited him well.
It was the fascination for flight that led to the dangerous experiments he carried out with 3 other researchers. Although he was the first to bail out, he and his descendents were unfairly saddled with the Corby Curse, which gave them the ability to change into corvid birds.
A note on the Corby family name:
The Corbies are descendents of European slaves bought free by the monastery of Corvey, near Hedeby in present-day Sleswich-Holstein.