No, you didn’t get anything wrong, I just decided to start with the 3rd section for now to skip the prologue, the part with the roman numerals, the chapter that’s for those players who want to read theory and more.

Here we’re going to cover all of the core of SEACAT right now, in a single blog post. That’s all that the skeleton of any rpg really needs, after all.

I’ve written this kind of post about three times already, for different books, editions, or unfinished versions. It’s really about clarifying basic assumptions behind a roleplaying game book, so that author (me) and players (both heroes and referees) are more or less on the same page.

I’m probably not going to write it all again, instead just revisiting and adapting this page as required.

1. Heroes and Referees

When you sit down to play roleplaying games at a table, who are you? There are two types of player in SEACAT—the heroes gallivanting around and their cat (referee) who runs the show.

The Heroes (aka. the players)

These players run protagonists through the game and sometimes a story emerges. Their primary imaginary characters are called heroes. The heroes are out for adventure, loot, and revolution. Don’t assume they’re good. Heroes are not good; they’re excessive and over the top. Over the top is good. Players can swap out or replace heroes from session to session. The heroes can die, retire, leave, or just take a vacation for a while. Use hero sheets to record their attributes.

The Cat (aka. the game runner aka. the Ref)

I’ve been running roleplaying game sessions and campaigns for decades, and if you’ve ever tried your hand at it you’ll know that terms like “dungeon master” or “game master” are misleading. You’re no master—maybe a game runner or referee. But even more than that, you’re the member of the band that gets the evening organized, prepares a few hooks, and sets the beat for the game. You’re like the bass player of the roleplaying group. You’re cool, but you’re coolest when you help everyone play and shine together.

2. The dice are not your masters

At the heart of roleplay is a conversation between players which creates a shared world. When common sense, or uncommon, dictates a result, don’t bring dice into it. When outcomes are uncertain, the referee suggests a probability and lets the player decide to roll or not for their hero. However, once the dice do roll on the table, they are the oracle and they determine outcomes.

3. Classic polyhedral dice

SEACAT assumes you have a couple of sets on hand, from d4 (4-sided) to d20 (20-sided). Sometimes it mentions strange dice, like a d40. Use a digital die roller or a creative combination of dice.

That said, you could use other dice. Sure, probabilities would change, but that’s no big deal if you’re consistent.

3.1. Glorious d20

The twenty-sided die (d20) is the core die of SEACAT’s descriptive mechanical skeleton because it is my favorite polyhedron and because it has a comfortable, flat spread of probabilities in easily digestible 5% chunks.

4. High is good, low is bad

Throughout the text, from encounters to random results.

Consistency!

5. The stat test (the core mechanic)

Whenever the d20 comes out to determine uncertain outcomes, that’s a test.

Test: d20 + Stat + Skill over Target.

A common format is ‘easy Charisma test’—this means rolling a d20, then adding the Charisma stat and a relevant skill to beat an easy target. What’s a relevant skill? Anything that makes sense in the context. Archaeology might help with deciphering old runes in a tomb while tea-leaf reading might well apply in a tea ceremony test.

The target of a test is described as trivial, easy, moderate (or average), difficult (also hard), or extreme. A hero rolls over a target number to succeed. A target number can be fixed or a little bit random.

This table looks more confusing than it is. Let’s break it down. First, the table is targeted at the the ref to help them translate words into numerical targets. This isn’t a table most heroes will ever have to see in play.

Target: example words for describing how hard it is to do something. As the ref you can use other words in actual play to introduce variety. Super easy, barely an inconvenience, rather tough, nigh impossible, somewhat annoying. If heroes ask for the target number, give it to them. Let them roll dice knowing their odds.

example words for describing how hard it is to do something. As the ref you can use other words in actual play to introduce variety. Super easy, barely an inconvenience, rather tough, nigh impossible, somewhat annoying. If heroes ask for the target number, give it to them. Let them roll dice knowing their odds. Fixed: this is a series of prime number targets, ranked from easiest to hardest. The moderate target is 11 since the smallest value of a skill is 2. Every skilled hero thus always has better than even odds of succeeding at a moderate test (at least 55% to be precise). Otherwise, might as well flip coins.

this is a series of prime number targets, ranked from easiest to hardest. The moderate target is 11 since the smallest value of a skill is 2. Every skilled hero thus always has better than even odds of succeeding at a moderate test (at least 55% to be precise). Otherwise, might as well flip coins. Flat: here the referee has a list of die rolls they can make to generate a random target number based on a descriptive difficulty. A referee can roll dice to set precise difficulty targets so that neither they nor their players know precisely how hard a given test is. These rolls are called flat because they’re all made with a single die, so their probability spread is flat—each result has equal odds of ocurring.

here the referee has a list of die rolls they can make to generate a random target number based on a descriptive difficulty. A referee can roll dice to set precise difficulty targets so that neither they nor their players know precisely how hard a given test is. These rolls are called flat because they’re all made with a single die, so their probability spread is flat—each result has equal odds of ocurring. Curved: ok, this label is imprecise. Still, it gives the approximate number of d6s a referee can roll to generate a random target number. Alternatively, it gives the number of dice heroes would roll in a roll-under ability score mechanic as used in some OSR games.

ok, this label is imprecise. Still, it gives the approximate number of d6s a referee can roll to generate a random target number. Alternatively, it gives the number of dice heroes would roll in a roll-under ability score mechanic as used in some OSR games. Example Procedures: this is just more clarification on difficulties.

Only use tests when they make sense, when possible outcomes make a meaningful difference. Trivial tests are for situations where failure will start a chain of hilarious and unexpected events because the heroes are pushing their luck a bit too much.

For example, driving down a narrow lane wouldn’t require a test, but if six tipsy heroes are in a stolen yugo fleeing a pack of zombies that attacked a mafioso’s wedding party, then a trivial check might be required to avoid smashing into a badly parked jaguar or beemer.

Use natural language! Jargon and complex or confusing terms make it harder to learn roleplaying games for no good reason! These are not hard games.

5.1. Relevant test

Sometimes, if you really can’t think of an optimal way to overcome a challenge, just use the phrase ‘relevant test.’ This means that a hero can use any combination of stat and skill that makes narrative sense in the circumstances.

5.2. Over-defined Tests

Some tests, particularly Misfortune tests, have multiple fail and/or success results—you’ll recognize them by relevant tables of outcomes. They do not require a descriptive target beyond, “just roll high. High is good.”

An over-defined test is a good way to add mood to adventures and special locations, but for most play you don’t need one. It’s more a thing for module and setting writers to consider, than for referees to implement in prep. Let’s make that even clearer: don’t prep tables like this unless you really enjoy doing that!

5.3. Ones fail, twenties succeed

In every d20 test, if the die rolls and turns up 1 or 20 this is a ‘natural 1 or 20.’ These always fail or succeed. If failure is impossible, a roll should never be required. Don’t try to build tension with fake rolls.

6. Advantage and disadvantage

This is one of the better rules around and SEACAT uses it broadly, for every die roll from a d4 to a d100. Advantage (↑a) means rolling an extra die and taking the better result, disadvantage (↓d) rolling an extra die and taking the worse result. Advantages and disadvantages cancel each other out.

6.1. Boons

Boons and blessings, unless otherwise specified, manifest mechanically as advantages heroes store and use when they like.

If a group want to implement banes, for disadvantages that the heroes store, they can choose to let the heroes carry them and use them at their discretion, or pass them to the ref, who can drop them on the heroes at the most inopportune time. This is fiddlier and probably unnecessary.

~7. Consecutive Rolls

Sometimes a result in a table is written with a slash, e.g. 20/20. This means that when you roll a natural 20 you roll an additional consecutive die, and if this is also a 20, voilá—you have a rare result. Additional slashes indicate additional yet rarer possibilities. This mechanic is a silly way to add rare results and recalls the days of 18/00 Strength.

This is an example of a mechanical mini-game that a group can use or not, and it won’t change the roleplaying experience much at all. It’s like spice—a weird mechanic here and there is fun, but overdo it and it’ll get old fast.

~8. Exploding Dice

Rarely you will come across another kind of consecutive dice, written with a little asterisk, e.g. d6*. Every time you roll a natural 6 on that d6*, roll an extra die and add the result. Repeat as long as you keep rolling sixes (or whatever dice you’re using). Exploding dice come into play with carousing and some weird artifacts—even if you forget this little rule, it won’t matter much.

Another weird unnecessary rule. This one works better with smaller dice. Ok, now a few summaries.

9. Six Stats

SEACAT plays with six stats: Strength, Endurance, Agility, Charisma, Aura, and Thought. A stat of 0 is the minimum for heroes, 5 is the maximum. They represent the natural aptitude of a character.

Think of a stat of 0 as representing an average bog-standard human, so heroes are better-humans. What’s the word … oh, right. Heroic.

10. Skills

Learned skills (represented by an inchoate series of descriptive skills which vary from setting to setting and over time within a campaign) define what a hero is good at. A basic skill starts at 2 and can go as high as 8 for an expert.

Consider that a moderate test has a target of 11. An unskilled hero, with no relevant stat has a 45% chance of success. A basically skilled hero (skill 2) has a 55% chance of success (they’re just about 20% better), a very skilled hero (skill 4) has a 65% chance of success (about 45% better), and an expert (skill 8) has an 85% chance of success (about 90% better). Honestly, stack that with stats and advantages, and you’re well set for big differences in the odds. But … why are we even …

They’re also a very basic way to skin a setting (or dress-up a cat).

11. Abilities

Meanwhile, abilities represent … well … abilities acquired through any means that are outside the human norm, beyond what an ordinary human could acquire through simple theory and practice.

Heroes usually get one every level, and possibly more through adventuring, becoming more and more unusual and exceptional over time.

Here’s how to think of it: abilities are little packages of mechanics and flavor that expand (or break, if you prefer) the core mechanics and change how individual heroes interact with their worlds.

12. Strict Limits

The maximum level a hero can reach is 9. Their maximum total bonus (stat + skill) to any d20 roll is +13. The highest target number a hero can ever possess or set is 19—this includes defense.

Strict limits in a game of unbound imagination?!?

Yes. These numerical limits are built into SEACAT for a very simple reason. The mathematics of using a flat die mechanic (the d20) for randomizing outcomes breaks down when bonuses become significantly bigger than about one half of that die. The die becomes less and less relevant to play the bigger bonuses get. The same with targets. If target numbers get higher than the die used, it means more and more in-game situation no longer require dice.

On levels, my thoughts are related, but a bit different. I’ve rarely experienced a large-traditional-d20 campaign go much beyond level ten, but I have experienced the bloat that higher levels bring to the game. This is because the game increases variety and power by piling on higher numbers and more interlocking abilities and features. I prefer stranger and more powerful abilities available to heroes right from the start, with less complexity and bloat further along.

Ok, that’s it for the superbasics. 12 (or 10 if you drop the optional ones) guidelines and mechanics. Both numbers are attractive enough. Next time, another SEACAT chapter, with more commentary by Blue Skull.

—Luka

Now for a standard pitch closing. To support more of my creative rpg writing and art, the Stratometaship patreon is a good place to start. Alternatively, you can buy the .pdf of the Ultraviolet Grasslands at Exalted and on DTRPG. You might also consider the Slumbering Ursine Dunes books, which are heavily arted-out by yours truly. That link leads to What Ho!, by the way.