The Witch covers the Witch character class and the various traditions of witchcraft one might encounter in an old-school fantasy game. This sourcebook contains plenty of information for players and game masters alike, including new spells, powers, magic items, and monsters. Compatible with original Basic Edition fantasy games, or your favorite retroclone!
Tim's an excellent writer and his witch material is always entertaining. You can find plently of info to supplement the work at his blog, The Other Side.