Professor Quirrell
Reasoning: A strange card, representing gaining knowledge through personal surrender. Voluntary sacrifice, submission to a higher power, seeing things in a new light, and total relinquishment of the ego. This card is suspended in a moment, letting go of old habits and beliefs.
This is not a negative card. I just thought that Quirrell represents it well as he has voluntarily opened up his mind (and even his body) to Voldemort. He has left his old beliefs, and surrendered himself completely to the ideals and control of Voldemort, whom he considers a higher power. He is completely vulnerable, and in a weird way can be considered a martyr for his new cause, as he dies in the course of Voldemort's work.
In a traditional tarot deck, this is the Hanged Man.
Notes
This card had a difficult start. So difficult, that I actually entirely completed a version of it, then looked at it again, and realized it was completely awful in several ways. So, it was back to the drawing board (literally), where I came up with this. The idea is the same, but just technically improved.
I love his outfit (heavily inspired by the movie, the costume from which I adored).