OSE Month is a group-collab project led by Exalted Funeral and Necrotic Gnome, featuring a new 176-page OSE book — the Demonic Grimoire — and sister projects from other renowned creators in the OSE community.
The theme of OSE Month 2026 is: DEMONS! Get ready for hordes of new monsters, adventures set in the realms of hell, fiendish new character options, and lashings of blood-dripping art.
What is the Demonic Grimoire?
A hotly anticipated major rules supplement for Old-School Essentials, expanding the game with demons, cults, and dark magic. Contained within this 176-page tome:
8 demon lords, detailed with their cults, minions, spells, and hellish domains.
60 new monsters, from lowly tormented souls to mighty lords of hell.
4 new classes: chaos knight, cultist, demon hunter, tiefling.
70+ new magic items of fiendish power.
Demonology: magic circles, summoning, demonic pacts, familiars.
Referee advice for building demonic campaigns.
120+ black & white illustrations, including a fully illustrated bestiary. Art by Lucas Korte, Kennon James, Tony Hough, Matt Stikker, and other leading old-school artists.
Pristine control-panel layout to maximise ease of reference and minimise page flipping.
We've partnered with StartPlaying to celebrate OSE Month 2026, with a horde of experienced referees running Old-School Essentials games online. The chosen referees even have access to our new demon-themed adventure, Golden Lies! Jump in for a chance to experience it first hand.
OSE Month special offer! Use code OSEM6 at checkout for $10 off your first game on StartPlaying during the event.
New to Old-School Essentials?
OSE is an award-winning role-playing game of fantastic adventure, monsters, and magic. Players delve into forbidden crypts and forsaken ruins, explore haunted forests and perilous mountain ranges, sail the high seas in search of lost lands, recover fabulous treasures, and unearth secrets of ancient magic.
Developed by Necrotic Gnome and published by Exalted Funeral, Old-School Essentials is the most popular retroclone based on the 1970s–1980s editions of D&D. The great wealth of adventures, settings, and rules supplements published for games of this vintage can be used with OSE without conversion.
Pairing old-school rules with modern, easy-to-reference layout, OSE is fast, fun, and deadly. You can read more about the game at necroticgnome.com.
The latest printing of the OSE core Player's Book and Referee's Book (2026 update) will be available as part of this campaign, alongside the Demonic Grimoire supplement.
