Practitioner of black magic

HEXER

This spellcaster’s name sounds like someone who might cast a six-letter curse.

"Hexer" is a straightforward term for someone who practices black magic, often casting curses or spells. The word hex itself refers to a magical curse, so hexer simply means the person doing the hexing. It’s a less common but fitting answer for this clue, avoiding more typical terms like witch or warlock to keep the puzzle fresh.