The Necromancer's Retreat

From publisher blurb: Issue #14 of Populated Hexes Monthly remains in the Fenimil Swamp and features the lair of a reclusive necromancer as well as a playable necromancer class for Old School Essentials and similar games, inspired by Garth Nix's Abhorsen series. Populated Hexes Monthly is also available in staplebound format singly or as a monthly subscription on the author's website.