Creation of a TTRPG using Mongoose


Hello people of Mongoose,

First as a preface,

A friend of mine whom I had played various TTRPG’s with over the last 25 years passed away last year but before he did, I let him know I would ensure our worlds, characters and history that has been built up would remain. That is the main driving force of the creation of this two-part TTRPG I am creating and wanting to use Mongoose system as the core of it. I mention this because there will inevitably be people talking about how no one would play it, or it is a bad idea. My motivations are not financial, this is purely for the love of TTRPGs. The second part is only in passing as it may not be created as a great deal of the first part is the Fantasy version.

So before getting into what it looks like so far, I wanted to ask currently just one question which naturally is the most important one.

How can I ensure that I am keeping inline with your current open gaming license so when I do eventually get to publishing work, I haven’t violated anything, and you get mad at me. I definitely don’t want Mongoose to be mad at me. I love Traveller 2nd edition. I have spent entire evenings building star systems and using excel to help me create random star system maps.

Let me share the gist of this TTRPGs premise. Think if the Universe was a person like Marvels Eternity. But instead of standing in some blank nowhere the embodiment of the Universe is in a Lovecraftian void filled with horrors beyond imagination that would love nothing more than to eat said Universe. So, this Universe finds another Universe like itself, so they stay close together for protection. One being primarily a fantasy universe and the subject of part one of this TTRPG and the other being a Sci fi / super heroic Universe which would be part 2 if that ever happened.

The below is still work in progress and not yet play tested. Getting closer every day.

So, within the Fantasy universe which is part one I have been diligently working on expanding and making some changes on what exists with the core rules. First is Characteristics some original, some changed, some new. All stats will range 0-23

Intuition (or Psionics if the character unlocks their Psionic potential.)
Spirit (or Arcane/Chi if the character follows a Monk or magical path.)

Social Standing would be a static score that would be affected by their Background/Career events etc.

Social Standing
0Outcast, hated, reviled, possibly attacked on sight, considered scum.
1 to 2Very Low at the level of street urchins, common criminals, pirates, slaves etc.
3 to 5Impoverished working class, the skill less and rankless , the oppressed.
6 to 8skilled professionals, those who work hard for a living. This is where a majority of civilized people are.
9 to 11Highly skilled professionals and those who work directly for the nobility and have some influence or inner knowledge on how those higher up socially work. Some small business owners. Powerful Knights
12 to 14Barons, partners or franchise owners of a business, people known across the world. Guild leaders.
15 to 17the rulers of city states and small kingdoms, celebrities you would have to live under a rock to not know who they are. Heroes of a kingdom that hang out with other heroes of other kingdoms. Nobles capable of telling other Nobles what to do.
18 to 20Count, owners of large business empires or multiple guilds, rulers of large kingdoms, people known on other worlds and the outer realms. Crown royalty.
21 to 23Emperors of large empires or even Gods, People whose name even some gods in other Universes know.

Wealth would be used as well instead of coin counting. Starting Wealth is determined by Background, gauge of lifestyle they are capable of, how much of a large purchase they can do, and generally month to month how much pocket money they have.

Destitute not a single thing of value in your name.
Lower Class (-2 circumstance penalty to Social Standing)
Lower Middle Class (-1 circumstance penalty to Social Standing)
Middle Class
Upper middle class (+1 circumstance bonus to Social Standing)
Upper class (+2 circumstance bonus to Social Standing)
Wealthy (+3 circumstance bonus to Social Standing)
You likely own everything on the planet.

Also, health points.

Health Points All Physical Characteristics added together to create Health points.

Example: Str: 6, Dex: 9, End: 10. Total health points: 25 breaks down by three from Healthy to Injured, and Critical.

Divide by three round up. 25/3: 8.33 so 9. Healthy 25, Injured 16, Critical 7.

Health 25 to 17 No penalties proceed as normal.

Health 16 to 8 DM -1 all rolls

Health 7 to 2 DM -2 all rolls

Health 1 DM -3 all rolls Movement is halved.

Health 0 Unconcious/dying

Mental Health works the same.

Besides skills these characteristics would be used in Social combat. i.e arguing, negotiation, leading troops if just a few skill rolls simplify a situation too easily.

Further, these would be considered your physical skills when Dreamwalking or otherwise traversing the Astral plane.

Mental Health points would operate similar to Health points but going to 0 can result in catatonic or coma like state and brain death. Your body is a healthy shell.

Luck will have some special uses.

How fortunate you are in life. To be used to resist death, effect random chance, augment your rewards, mitigate your misfortune. A finite resource that is difficult to gain. (oddly enough, you can get more by being lucky or even taking chances.)

And when your dying.


Attacks on dying target kills them.

Damage from a single attack that is larger than Targets full endurance score kills them if it takes them to 0 health.

If no damage is taken and if not stabilized a dying target must make roll with Luck vs TN: 6+ to self-stabilize.

Failure means your luck goes down by 1. Failing by 3 means your luck goes down by 2. If your Luck runs out, you die.

If success by more the 3 Target goes to 1 health and is conscious.

Luck will return as you heal but it will go down by 1 permanently. Sooner or later, luck always runs out.

I also have a premise for Thresholds.


The idea being some people seem to just shrug some things off like say the cold. So their attributes will create thresholds like Cold 1 meaning they take no penalties when in an environment of the first band of low temperature. While someone else with no Cold threshold needs to wear a coat. That’s just a rough example.


I have 9 races counting humans.

Humans have the default max of 6 career terms.

Non Human Races gain additional traits but max of terms is 5.

Optionally detrimental trait sets for the races can be chosen to get back the 6th career term.

On Age. All Races reach adulthood about generally the same time however some races age considerably slower at Middle age.

Cat of Baast, Halflings, Minotaur and Orcs all age on par with Humans dying of old age usually around a century.

Dwarves and Gorgons remain middle aged for about three centuries living as long as five centuries before dying of old age.

Ryujin will remain Middle Aged and not physically age but dying of old age around a thousand years.

Elves never die of old age but hear the call of the Primordial Garden where their Gods rest.

The call become harder to resist those who go to the Primordial Garden transform into Fey.

Age is placed in Band categories instead of specific numbers since time can sometimes just have no meaning.

Example Race.


Dexterity -1 Endurance +2

Base Race Traits

IR/UV Vision

Resilient: To Poison

Profession (0) Dwarves are driven to find work at a genetic level.

Athletics 1 (Strength)

Natural Heavy Gravity Adaption

Optional Traits at -1 Stat per

Navigator (0)

Great Beard +1 Personality

Daunting: Endurance +1

Stone Skin: Armor 3

Then there are the lineages.

Such as Infernal Blooded whom you can have the base with no penalty its mostly cosmetic or some trait/drawbacks that balance each other or you go for the stronger lineage which gives you stronger benefits but at another career term penalty or other drawbacks.
Case in point a lesser Infernal Lineage may just have the look and some good eye sight but no draw backs while a stronger one has actual wings, can use claws like a weapon but they also have a max career of -1.

You can also have multiple lineages if you want the additional draw backs and also need to roll on the extra mutation chart. So you could have someone who starts out their character with no career and they are some sort of Elven Infernal, Celestial, Dhampir, Dragon blooded abomination that’s likely purple and has a tentacle somewhere.


Career Assignment





Arcane Student









Celestial Pact

Eldritch Pact

Infernal Pact










Heavy Cavalry












Martial Artist

Chi Master


























Post is already too long but these are the working ones.

Creation premise is

  • Pick race
  • Pick background package (roll for childhood events)
  • Pick pre career and roll for events
  • Enter career proceed as one does normally in Traveler.
Modification being events, mishaps, and life events come from three 66D charts


Works in three ways.

First is similar to how Psionics work but with a lot more. Boom. A sort of build a spell or add on details with more cost.

The second is using points to activate certain traits that are available to choose from.

The third way is essentially skill tests. Druids don’t make nature hit you with lightening, they ask Nature to hit you with lightening. The True Namer path will be especially interesting once I get it fleshed out.

An example of a spell for say Necromancy’s animate dead is.

Shania the Apprentice Necromancer has Necromancy Rank 0 and intellect of 12 (+2)

A corpse is brought in that died a few days ago so more than a day less than a week.

She is told to make a zombie.

Zombie is TN 8+ and costs 2 Arcane points. She rolls max a total of 14! Minus the Target number she made it by 6

which is 2 degrees of success so the Zombie will be active for two hours.

If she paid 6 additional points, she could increase the Duration base to a day and the zombie would be animated for two days.

Paying 1 Arcane point at the end of a duration will reset its duration.

At the end of two days Shania can pay 1 point and keep that zombie for another 2 days.

There are also rituals that are either devoted to a specific career or ones anyone can do if they fulfill the terms correctly and do the skill test chain right.

This is just all a real sample I also have, Monsters in tiered lists with traits that are based on what sort of environmental and behavioral qualities they have, Guilds and the methods by which you join, what you gain from them and their ranking system, Equipment has quality levels, Skills have traits you gain at ranks 3, 5 and the max 7. Some skills have been changed or expanded upon for a fantasy world. And the lore is based off of 25 years of weekly roll playing so it’s, pretty extensive.

This is really all to show you I am serious about building this TTRPG. However, as my question says. I don’t want to violate any terms so I am hopeful for guidances to be able to use what I can use as Mongoose’s system is of course amazing and I don’t want to do anything wrong. I have 11 excel sheets full of stuff I have built up over the last year and every day it gets bigger.

Thank you for your time.
Sorry, the above was written while half asleep.

I am about 3% done with the whole thing. My intention ultimately is possibly 2 books the first being the core and the second being the atlas/monster book. Further looking into also having a character maker made along with it. I have a list of close to a thousand tasks in order to get this thing off the ground so my brain is tired. Ultimately when published it will be as low a cost as I can make it to break even then give myself and my silent partner some pocket money. Though ultimately its the thing itself that matters more to me then as a item of profit. Which was what I was meaning to say.

It is about 7% close to being play tested and as long as I do about 20 steps a week I will be to a play testing point by September. Eventually I also have to look at art, book design, and a ghost writer for the lore as my writing skills are not what they once were. But the idea involves a number of things towards world building, customization, void ships (fantasy space craft) And Dyson city (if a magical death star was used to fight eldritch horrors) having the main world be the center of the web with broken worlds scattered about in the void, with gods, titans, primordials and things with copious amounts of tentacles running amok.

New ideas are coming all the time. I had just been thinking about what if certain spells being treated like equipment. Is one I am mulling over. The idea further being that this is just one universe and there is another which is more Traveller like in its future while its past is more super heroic like and once that is all hashed out you basically have a multiverse of different genre with crossover possible.

though the idea is to keep the math easy, the combat fast and ensure even at high levels of power it doesn't get bogged down. I loved playing at high levels in some ttrpg but one fight took three hours and that was because of all the ridiculously high numbers. Also making the game as all encompassing as I can because once its all done I am done. brain is getting older and more tired.

Also my thought was to have an electronic character maker made with it. i imagine that will cost me a bit but I think at least with tech these days its imperative to include electronic tools especially to help make playing as easy and fun as possible. Well that was just something I wanted to add.
Hey there,

Have a look at our licensing page and see what seems right to you:

At first glance, the Fair Use Policy might be best?
Thank you again for your help in this. I have looked over the information. If I understand it all.

When I complete my TTRPG if I do so in a noncommercial way it is allowed under the Fair use policy. Specifically, after Mongoose’s edition of Traveller are added in 2025 since that is what I am basing a lot of information off of.

However, If I wish to release my TTRPG I would want to be under the Traveller Compatibility licence but to do that. I would need to be an established publisher. Or have a thriving lot of products on the TAS Programme.

Well, if it ends up having to be free to be released then that is what it must be since it is a project from the heart. Though I would like to make it a commercial release at least to help mitigate costs of the art, design, editing etc. And, if it makes money, I can go back to my doubting friend and be especially smug.

So, since I am not an established publisher and while I am going to formerly create an LLC for this release, I imagine established has a certain definition.

My next avenue would be then to take part in the TAS and have a “thriving lot of products”
Well after 25 years of roleplaying weekly and daily, I have a lot of ideas, I suppose Its time to see if any of them are good ones.
But one must ask then… what is a “thriving lot?”
Because I could make a lot of things. My number of home brewed aliens, ships, worlds, adventurers, and so forth is abundant. (Besides work I live in TTRPGs so I have plenty of time.)