Shadowdark vs Mörk Borg vs Old School Essentials
The short answer
Pick Shadowdark if you come from D&D 5e and want what you know about a d20 to keep its value, with real danger back in the dungeon. Kelsey Dionne kept the familiar maths and cut the character building. Your torch burns for one hour of real time, so the clock on your table is the clock underground.
Pick Mörk Borg if you want doom, filth and speed, and like the idea of a world already counting down. Four stats, savage rolls, characters who die in the first room. An evening is a full arc.
Pick Old School Essentials if you want the original 1981 rules with nobody’s mood painted over them. Gavin Norman rewrote Basic/Expert D&D for clarity, not flavour. It is the purist route, and by a wide margin the best organised of the three.
What these three games have in common
All three sit in the OSR corner and agree on more than their covers suggest. Characters are fragile, and a first level adventurer can die to one lucky goblin. Making one takes minutes, because there is almost nothing to build. None of them carry skill lists or feat trees, so what your character can do is mostly what you describe.
They also agree on what a session is about: gold and survival, not balanced encounters. All three expect a group to walk away from fights it cannot win and to ask what a room looks like instead of rolling a check. Material travels between them, so a dungeon written for Old School Essentials runs in Shadowdark with a few numbers changed.
Where they really differ
The core roll. Shadowdark is a d20 roll high system with ascending armour class and advantage or disadvantage, exactly the shape a 5e player expects. Mörk Borg has four abilities, Agility, Presence, Strength and Toughness, modifiers between minus three and plus three, and one d20 test against a difficulty number. Starting hit points are Toughness plus 1d8, so a character can begin with one. Old School Essentials keeps the 1981 maths intact, descending armour class and all, with an official ascending option beside it, and there dwarf, elf and halfling are classes rather than ancestries.
Time is a rule, not a mood. In Shadowdark a torch lasts one hour of real time. When it dies your characters see nothing and the monsters see everything. In Mörk Borg the group picks a die at the start of the campaign and the referee rolls it each dawn; on a one a misery falls on the world, and the seventh ends it. Choosing a d100 or a d6 is choosing how long your world lives. Old School Essentials uses the classic dungeon turn: ten minutes per turn, wandering monster checks on a schedule, light and rations on paper.
Magic is a gamble in two of the three. Shadowdark casters roll against ten plus the spell level, and a failure means the spell is gone until they rest. Mörk Borg has no spell list, only unclean and sacred scrolls; a bad roll costs hit points and can trigger something worse, and heavy armour shuts your powers down. Old School Essentials is properly old fashioned: spells are memorised in advance, and a first level magic user has exactly one for the whole day.
The book as an object. Shadowdark is a 330 page A5 sewn hardcover, one topic per spread, and it reads like a manual in the best sense. Old School Essentials splits its rules over five slim hardcovers on the same principle, and is arguably the most usable rulebook in the hobby. Mörk Borg is the opposite on purpose. Johan Nohr designed the pages as an art object: neon yellow, ink splatter, rotated columns, fonts that change without warning. Some people find that thrilling. Others find it genuinely hard to look anything up mid session and end up writing their own reference sheet. Both reactions are normal, and it is worth knowing which one you are.
What you get to run. Mörk Borg hands you a complete dying world, with named regions, prophecies and a tone you either adopt or fight. Shadowdark implies a grim world without insisting on one and leans on generators and its Cursed Scroll zines. Old School Essentials ships no setting at all: no map, no pantheon, no default region, because the point is the engine. If you want a world handed to you, that is a real drawback.
What it feels like at the table
Shadowdark feels like a countdown. Someone glances at the timer, says there are eleven minutes of torch left, and the party stops arguing about the locked door and starts deciding. Nobody reaches for the book. The tension comes from light and low hit points.
Mörk Borg feels like a punk gig. A character dies before the first scene ends, everyone laughs, and the player rolls a new wretch in two minutes. Then the calendar rolls a one, the sun goes wrong, and the evening gets an ending nobody planned.
Old School Essentials feels like a heist. Ten foot poles, a marked map, a long debate about whether to open the door at all. Combat is short and frightening, and most of the session goes into avoiding it. Coming back up with the loot and everyone alive is the win.
What you actually need to buy
For Shadowdark one book does it: the Shadowdark core rulebook at €59.95 holds classes, ancestries, magic, monsters and referee tools. To test the water, the Quickstart Set at €24.95 gives you two 68 page booklets, eight ready made heroes, levels one to three and the adventure Lost Citadel of the Scarlet Minotaur. For solo play there is Solodark at €12.95.
For Mörk Borg the core book at €29.95 is the whole game. There is no starter box. If the engine appeals but the dying fantasy world does not, Pirate Borg at €39.95 and Cy_Borg at €49.95 run the same rules in the Dark Caribbean and in a collapsing cyberpunk megalopolis, both standalone.
For Old School Essentials the Classic Game Set at €74.95 is the entry point: five sewn hardcovers covering characters, magic, adventuring, monsters and treasure, with a cover by Erol Otus of the original 1981 boxes. It is the most expensive and the most complete, with seven classes, over a hundred spells, more than two hundred monsters and over a hundred and fifty magic items. Beyond that, all three need dice, paper and a referee.
Choose Shadowdark if ... / Choose Mörk Borg if ... / Choose Old School Essentials if ...
Choose Shadowdark if your group plays 5e and wants a lighter game without learning a new language. Choose it if you want the danger of old school play but not the bookkeeping of descending armour class. Choose it if your sessions are short and the torch timer can set the pace. Choose it if you referee with almost no prep.
Choose Mörk Borg if you want one shots and short brutal arcs instead of a campaign of years. Choose it if your table loves black humour and does not get attached to characters. Choose it if aggressive book design excites you rather than annoys you. Skip it if you need to find rules quickly under pressure, and skip it if a dying fantasy world is the wrong tone; Pirate Borg and Cy_Borg give you the same engine in a decor you may prefer.
Choose Old School Essentials if you want the actual 1981 rules rather than an interpretation. Choose it if you own old modules and want to run classic dungeons as written. Choose it if you want every procedure findable in seconds. Choose it if you intend to play for years, with strongholds and wilderness travel at the far end.
Where to start at Netherbook
If Shadowdark is your pick, start with the Quickstart Set or go straight to the core rulebook. Our Shadowdark starter guide sketches the game first. The rest of the line sits in the Shadowdark collection.
If Mörk Borg is your pick, the core book is all you need, and the Mörk Borg starter guide explains a first session. The Mörk Borg collection also holds Pirate Borg and Cy_Borg, each with its own guide: the Pirate Borg starter guide and the Cy_Borg starter guide.
If Old School Essentials is your pick, the Classic Game Set is the one purchase, and the OSE collection holds the rest of that line. Still weighing this whole corner of the hobby? Our OSR collection gathers it in one place.