Sebastian is an extroverted boy whose twin sister Anne suffers from debilitating curse. He's convinced that her last hope for a cure lies in the Dark Arts, and he's determined to find it. He's a driven Slytherin with many secrets. He and Anne were raised by their uncle Solomon, a former Auror. While Sebastian's aims and goals seem well-intended, he's acting questionably to achieve them. He's compelled by the idea that magic is a tool, rather than something good or evil.