A comparative exploration of OSR RPG Systems - Maze Rats

Posted by Panayiotis Lines on

In this series of blogs we're exploring the various OSR RPG systems in the community and how they compare to one another and the original D&D rules.

Last week we looked at Into the Odd by Chris McDowall

This week we're looking at Maze Rats by Ben Milton (Questing Beast).

Maze Rats by Ben Milton (Questing Beast) is a fantasy adventure roleplaying game and hack of Into the Odd.  It pitches itself in many ways as a versatile toolkit as much as it is a system in its own right. The rule book is a slim 12 pages and many of those are lists of random tables, with arguably around half being devoted to the actual core rules of the game. There's no art either which densely packs as much content as possible in its small number of pages. Within is a tightly distilled rules package for running fantasy adventure games that follow many of the core principles of OSR games. As a note, unlike games such as Mausritter, you do not literally play a rat or equivalent in Maze Rats.

Character’s within Maze Rats are built out of 3 abilities, Strength, Dexterity and Will which are rolled randomly using 1d6 with a range from +0 to +2. A roll of 1-2 = +0, 3-4 = +1 and 5-6 = +2. Strength represents raw power, stamina and resilience, Dexterity represents speed, agility and precision and Will represents force of personality, perception or willpower. This mirrors the 3 stats within Into the Odd. Strength and Constitution are tied together in this respect with Will broadly representing Wisdom, Intelligence and Charisma from original D&D. 

This stat generation method is a much more simplified variant of the classic 3d6 down the line that we see in Original D&D as well as retroclones such as Into the Odd of which Maze Rats is based. It purposefully omits the ‘ability score’ entirely, going straight to the modifier in a similar way to systems such as Mork Borg. The range from 0 - +2 is a low curve too that also omits negative modifiers with characters at best being ‘average.’

This ties into the closest the game gets to a ‘core’ resolution mechanic which is the Danger Roll. Maze Rats notes that a character's action should mostly be resolved via description. This is in keeping with OSR principles. When an action is risky or difficult to resolve through description two six-sided dice are rolled and an appropriate ability modifier is added. If the total is 10 or higher the action succeeds. This eschews the d20 typically used for similar checks such as saving throws in other systems. The low modifiers combined with 2d6 bell curve keep the dice relatively stable and predictable in comparison.

Chances of avoiding danger by rolling the die in Maze Rats are low. You have a base chance of 16.6% to avoid danger, a 27.7% chance with a +1 bonus and a 41.6% chance with a +2 bonus. This is purposefully designed to discourage players from wanting to roll dice to resolve game situations in favour of simply describing what they do. The OSR principle found within the Principia Apocrypha of Player Ingenuity over Character Ability taken to its logical ends. Whilst some may feel this harsh, you have to think of it in terms of avoiding a danger you already got yourself into rather than actively doing something you’re skilled at. The skill focus in OSR games is intended to be on the player and their actions rather than the player's character and their bonuses and abilities.

That being said, there is an ‘advantage’ mechanic, most often known from 5e D&D, which allows you to add an additional die to the roll if the situation calls for it. This increases the base odds to a more comfortable 62.5% This again encourages player creativity in coming up with ideas that provide advantage, it also serves as another way to work out if you need to roll a die or not. Maze Rats notes you can only apply one extra advantage die to a roll and if you feel like multiple advantage die could apply in the situation it’s likely you don’t need to roll at all as the situation isn’t risky. This is a great rule of thumb that can be applied to any system with an advantage mechanic or equivalent.

In addition there’s a mechanic for opposed rolls where you roll 2d6 and highest wins, which is simple and covers most of the things the danger roll doesn’t.

Keeping a game to one die type is a neat way to make it simple and easy to run too. This resolution method also mirrors Into the Odd as well as The Black Hack in that the majority of rolls are effectively ‘saving throws’ which makes it easy to work out when a roll is appropriate or not as you simply have to ask whether someone is in danger. As the name ‘danger roll’ succinctly implies.

Attack rolls make use of the same 2d6 mechanic, adding the characters attack bonus then comparing it to the defenders armour rating. If the total exceeds it the attack hits. This is somewhat similar to the more traditional d20 roll against Armour Class found in D&D. Base armour in Maze Rats is 6, light armour is 7, heavy armour is 8 and shields grant a +1.  That means the base chance to hit an unarmoured combatant without a modifier is 58.3%, whilst hitting someone in heavy armour is 27.7%. To compare this to Moldvay Basic D&D there’s a 55% chance with no modifier of hitting an unarmoured target and a 35% chance to hit a target in Chain Mail. 

A shield is also significantly better in Maze Rats than in Original or Basic D&D. The +1 bonus a shield provides in D&D equates to a 5% increase in survival; however adding +1 in a 2d6 system can provide significantly more protection. For example carrying a shield whilst wearing Light Armour improves your survival chance against a standard attack by 16.67%. There’s also a common OSR house rule ‘Shields shall be splintered’ included in Maze Rats that allows you to destroy your shield and negate damage further amplifying the use of shields in this system. 

In simpler terms armour and shields seems to have a lot more weight in Maze Rats and the 2d6 dice distribution makes it more reliable in protecting you than they do in D&D which uses the much swingier d20.  

Many retroclones sprinkle in house rules within their texts and even now familiar rules like 'Critical Hits' were originally house rules that ended up being ported into the actual game systems being designed as thought on them evolved. 

A double 6 is in Maze Rats on an attack roll is a critical hit, this doubles the damage of the attack. Critical Hits dealing additional damage were not an official rule until AD&D 2nd Edition, at best being an automatic hit within BECMI. However they have often been a house rule and are included in many retroclones, with games like Dungeon Crawl Classics going to town with critical hit tables. The natural 20 you would typically need to crit provides a 5% chance compared to a 2.7% chance of a critical in Maze Rats. A 5% chance can feel a little high in a system designed to minimise wanting to roll the die so this double 6 result fits. 

In terms of damage this is worked out by calculating the difference between the attackers die roll and the defenders armour value. Heavy weapons deal an additional point of damage to differentiate them. Again a clean system that means you can resolve an attack and the damage with one die roll as opposed to separate damage die which Original D&D as well as many other systems opt for.

Initiative in combat is group based as in Basic D&D, with whoever rolls highest on a d6 going first. This is re-rolled each round to create variety in combat. Typically characters can move and do an action like attack or cast a spell.

In practice combat is going to play out in a quick and deadly fashion. Maze Rats is still a highly lethal game despite the more consistent dice mechanics, characters are dead when they hit 0 health, with characters having 4 HP to start. Recovery is 1 HP when a character stops to eat and 1 when they get a full night's rest. This is in many ways harsher than even Original D&D  where you at least had a chance of starting with more than 4 HP through your hit die roll and con bonus. As a result combat is still best avoided.

In terms of character creation after rolling stats your character starts with 4 HP and you pick one feature from a small starting list. Your health is not rolled randomly and is always a static amount. Four is the rounded up average of a d6 so in this respect Maze Rats mirrors the base d6 hit die for every character in games systems such as Into the Odd or Original D&D. Both these systems and many more choose to randomise the amount, though often a common house rule is to allow characters to start on an average number to prevent starting characters with 1 HP so Maze Rats just ties this into the core. 

The features you can pick for your character include include a +1 attack bonus, a single spell slot or a small selection of ‘skill’ specialisations, for example you can pick 'Briarborn' and get Tracking, Foraging and Survival. Alternatively picking or 'Shadowjack' gains you the skills moving silently and hiding in the shadows. These skills simply give you advantage when you attempt them, a simple and clean way in this system to have a 'specialist' class. Skills aren't available to characters unless they choose these paths making characters who do stand out that extra bit.

These all effectively simulate in the barest way possible the fighter, magic-user and thief trio you’d find in old school Dungeons & Dragons.

You then roll for starting equipment or choose from a list which includes the likes of Horns, Hand Drills, Rope and all that other good adventuring gear. You pick two weapons from a small list of light, heavy and ranged weapons including Spears, Axes, daggers and crossbows, name your character and you’re done.

That’s it, there’s extra tables for some fluffy details such as your characters personality, mannerism, background and clothing but the core of the character you need to play can be made in a few minutes. There’s no demi-humans such as Elves or Dwarves in Maze Rats, one would assume your character is human but nothing is stopping you describing them however you want and indeed the game gives lots of tables for physical details to encourage that. 

If your character picked the spell casting option they do need to generate their spells before the game starts.

The spell system is similar to that in White Hack, spells are formed of combinations of either Physical or Ethereal Effects, Elements and Forms. There’s lots of listed keywords associated with them. A physical effect may be something like Rending or Shielding, an Ethereal Effect Nullifying or Soothing. A Physical Element Clay or Acid, an Ethereal Element Chaos or Light. A Physical Form Wall or Golem, an Ethereal Form Cloud or Vortex.

Spells are usually rolled randomly and once a spell formula is concocted and keywords rolled the spell is named and the referee and player discuss its effect. For example I roll ‘Ethereal Effect + Physical Element’ on the initial spell formula table. I then roll ‘Deciphering Sand’ on the respective tables.  Then we discuss what the spell does. Perhaps Deciphering Sand allows us to read magical symbols and scrolls, or reveals secret doors and passageways, or allows us to carve secret messages into earth. It's purely up to the player and referee. Spells take an action to cast and can’t be cast again until the caster rests for a full night.

This system again ties into the freeform and descriptive nature of OSR play, it's a big departure from the more familiar lists of D&D spells such as Magic Missile, Fireball or Sleep all set in stone with their effects but means that every time you create a spell in the game it's going to have a unique and never before seen effect. Maze Rats does also note you can use spells from outside the game too such as the D&D spell list however it would perhaps be a shame not to experiment with this creative and freeform way of doing it.

The reaction roll is at the core of how NPC’s interact with the party, these are rolled with a flat d6 and range from hostile, wary, friendly and helpful. This is swingier than the standard 2d6 reaction table with far more chance of a hostile or helpful reaction.

Monsters and NPC’s are statted out loosely though in a similar fashion to characters. They have health ranging from 1 hit die for a weak creature to 6 for a colossal one with the standard being 2d6. They have armour, attack bonuses and ability modifiers like characters and can potentially cast spells in the same manner. It’s left up to the referee how they craft the monsters but there is a series of tables given for inspiration.  These list various monster types such as aerial or terrestrial, traits, abilities, features, personalities, tactics and weaknesses which when rolled together can form some highly unique monsters with some imagination. For example a Hulking, Amphibious, Clawed, Ant that crackles with electricity, gangs up on it's prey with others from it's nest but has a weakness to birdsong. Clearly some kind of rubber clawed bird is it's natural predator. 

Alternatively you can keep things simple and create a Goblin with 1 hit die and +0 AB. In either respect Maze Rats is a system that encourages imaginative play and for everyone at the table to be loose with the rules but specific with their actions which fits the ‘OSR’ aesthetic to a tee.

Encumbrance is loose, Maze Rats says each item has to be recorded specifically where it’s worn whether in a backpack or belt. Belts can carry two items and it’s up to the group to decide what can reasonably fit in a backpack. It also takes 1d6 rounds to find an item in a backpack during combat but things on your belt which where you store items as important as how much you can carry.

Morale rules are importantly included and have become a key feature of OSR play. They work as a WIL based danger roll that an NPC or hireling has to make when in danger. Specifically when an NPC loses half of their force, or a leader dies or a single NPC loses half of their health. This is similar to the morale rules from Original and Basic D&D though replaces the 2d6 morale roll with a danger roll, which also happens to be 2d6 in Maze Rats. The base target number of 10 means enemies will flee less often in Maze Rats than in say Moldvay Basic where morale was based on the specific monster being fought with many having a range of around 7-8.

Having a simple rule you can apply to everything is easier than having to look up monster morale values and Maze Rats especially as Maze Rats doesn't include an extensive bestiary and relies on the GM to invent creations of their own.  Interestingly being attacked by magic is added as a potential reason to roll morale which gives spellcasters that added bit of power and fear and fits the implied setting where magic is rare and esoteric. 

Advancement uses a simple experience point system, you gain 1 XP for turning up to the game, 2 for overcoming a challenge and 3 for overcoming an impressive challenge. You need 2 XP to get to level 2, 6 to get to 3, 12 to get to 4 and so on up to level 7. Each increment provides +2 HP and alternates between an increased ability bonus and being able to choose to gain an additional attack bonus, a new path or a spell slot. This is effectively a simplistic 'multi-class' system with any character being able to dip into having a spell slot, or gain additional skills or just focus on beefing up their attack. There's no class system in the game and you're never restricted into one 'build' which fits the freeform nature of Maze Rats.

Beyond the core rules there’s some cracking good advice on running game within the rules. This includes rolling dice in the open, reward questions with good information and the more dangerous something is, the more obvious it should be. All great and useful principles for running Maze Rats as well as any other 'OSR' game or retroclone. There's also advice on running Dungeon and Wilderness based games, including how to structure out a hexmap, with each hex being 6 miles, and when to roll random encounters. This follows a similar structure to the rules found in Basic & Expert D&D. 

There's also lots of tables of equipment, NPC inspirations and names, missions, goals, secrets, relationships, wilderness regions, inn names and dungeon tricks, traps and layouts to round it all off. The system attempts to pack as much useful information as possible within its layout to make it a valuable reference during and out of play. 

Maze Rats is an incredibly clean and simple system to run and play, it further offers great referee advice and has a unique spell and monster creation system. Even if you weren’t to play it, borrowing the tables for inspiration in creating something unique for your retroclone of choice will certainly spice things up and as a result it comes highly recommended as part of your old school RPG library. 

Thanks for reading! If you're interested in a trio of old school fantasy adventures check out Albion Tales on Kickstarter.

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1 comment


  • I really should play base Maze Rats more often. There are so so many parts of it I really like (esp. the overspill to-hit = damage, and the procgen spells).

    Sean Smith on

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