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Benefits (and Drawbacks) of Compatible Math Between RPG Subsystems, Pt. 1
Most ttRPGs have subsystems to handle different tasks a character might attempt, or threats they might need to overcome. For example, a game might have a rule for seeing if an attack hits a foe, a different rule for seeing how much damage it does, and a different rule for efforts to heal the wound over time. Often these rules have some sort of mathematical underpinning tied to a random number generator (dice cards, and so on) that determines success. Sometimes the systems have compatible math… and sometimes they don’t. In this series of essays we’re going to look at the pros and cons of having subsystems be mathematically compatible, and what kind of design pressure may lead to each system.
Now, to be sure, these trends of mathematical subsystems that interact with some randomizer to generate values of success and failure are not universal. Some games have only a single system and it applies to the success or failure of everything. Others manage to model success without randomizers, or even math in general. As a result the observations in this essay don’t apply directly to all ttRPGs, but only to a (broad) subset of them. For example, Lords of Gossamer and Shadow is a diceless system that uses math differently than, say Fantasy AGE. Similarly, Dread does away with random success chances in favor of a tension-building minor physical challenge, and while it’s not quite accurate to say it’s math-free (as having to do something once, vs having to do it twice, is a mathematical concept) it certainly isn’t using math the way most ttRPGs do.
However, even if these game systems don’t interact with math and randomizers in the same way as the items I’ll be discussing in more depth, that doesn’t mean some of the same pros and cons may not apply. Especially for people interested in modifying existing systems (or wanting to try their hands at designing a system from scratch), thinking about how different kinds of tasks are resolved, and whether those resolution mechanisms should be based on the same underlying rules, is useful regardless of what the game mechanics in question are.
I’ll also note that I find examining lots of different game systems useful to gain a greater toolkit of ideas and mechanics I can use for my own designs. While some mix-and-matching might feel weird (I wouldn’t recommend adding a Jenga Tower resolution mechanic to a card-based ttRPG game… at least not in MOST cases…), often being aware of a wider range of designs can help inspire new solutions to old problems (or, at least, help see potential problems and unintended consequences in advance).
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The Battle Between Success, Improvement, and Options in ttRPGs
I could make a MUCH longer post about this… but it wouldn’t actually be much more informative. So here is the short version.

When playing ttRPGs, in general (and always within the context of preferred complexity, crunchiness, and theme):
*Players like being able to have meaningful choices in character design.
*Players like having meaningful choices in character actions.
*Players dislike a single tactic or build being sufficiently superior that other choices are perceived as sufficiently sub-optimal that it is dumb to use them.
*Players want to have a good idea of what their chances of success are.
*Players get bored if there is frequently no chance of failure.
*Players want their characters to be better at their core task than other player’s characters.
*Players want to be able to improve how good their characters are at core and non-core tasks.
When trying to design games that meet all of these goals, game designers run into issues. If a player has meaningful choices in character design, and has a good understanding of what their chances of success are, and has ways to specialize to be good at a core task AND has ways to improve, odds are there will be a single character build and/or tactic that is clearly superior to other choices. And, worse, it doesn’t matter if there isn’t REALLY an optimal choice, just if a group of players conclude there is one.
If you fix that by having elements of success be divided among enough variables that there are multiple ways to try to be good at something (for example, if in combat you can increase you chance to hit a foe but it reduces damage, or you can increase your attacks per round but it decreases your accuracy), many players end up not knowing what will actually increase their total effectiveness, and be dissatisfied if something they felt would be a big improvement doesn’t pan out in play. (And some players will apply excellent math skills to determine a given build or tactic is actually optimal, and that reduces fun even if they aren’t right).
If you fix that by reducing the number of ways you can improve a character’s success, OR by making multiple options be closely hard-coded to very similar levels of success, players often feel like they do not have meaningful choices in either design (since they can’t make choices to improve their chance of success) or tactics (since it doesn’t matter which tactic you use, as they are all equally successful).
If you fix THAT by allowing a character to constantly find ways to improve their odds of success in multiple tactic or builds, it can be possible for a player to have little to no chance of failure, and they grow bored. This is especially bad if those options are easier for some players to find than others, so one player almost never fails, and other players feel they are penalized for taking different choices.
Obviously this is a much more complex issue but the core set of opposed desires and solutions are extremely common, the battle between Success, Improvement, and Options in ttRPGs.
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Koufrawraiths – A simple d20 monster template
This is designed as a simple template for monsters in a wide range of d20 games. It has a horror/mystery theme, and the GM should consider its use carefully. Certainly it’s going to be as dangerous as a creature 1 level or CR higher, and if PCs do not yet know how to deal with it, it may be much more dangerous. On the other hand, a group could walk right past one and never know it, so it needs to be used in an intentional way with forethought, rather than as a random encounter.
Koufrawraith

A koufrawraith is a creature that exists in the dim fog between the waking world and the Plane of Dreams. They cannot be encountered by anyone fully in either realm, but do cross into any other reality where creatures able to sleep exist. Despite the name koufrawraiths are not necessarily undead, though undead koufrawraiths do exist. Many are hags, fey, monstrous beasts,and rarer examples exist as constructs, dragons, and oozes.
A koufrawraith’s existence can only be experienced by those who are fatigued or exhausted, but conscious. For any other creature, they cannot be perceived or effected, and the koufrawraith similarly cannot directly effect those who are ineligible to perceive it. It does perceive waking and sleeping creatures, but no action it takes (including things like casting spells that leave lasting effects, such as a wall of stone) can be perceived by, effect, or be effected by such creatures. Secondary effects can be–if a koufrawraith damages an exhausted person, the damage is visible and can be healed, but there is no evidence of how it was caused. Any effort to identify a koufrawriath from secondary observation or description suffers a -10 penalty.
Also known as sleepgaunts, koufrawraiths often prey upon lone insomniacs and those suffering great loss or toil. If feeds on the suffering of the tired, and prefers to hurt and frighten its food source, rather than kill them.
The ancient order of the Wearied Guard once drove koufrawraiths to near extinction, but once they were no longer a common threat, societies stopped supporting, or even believing, those who claimed their crucial work had to be done in the still of night, while bleary-eyed and staggering from fatigue.
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ShadowFinder Campaign Sketch
ShadowFinder is a concept for a Modern Urban Fantasy setting using heavily-modified Starfinder.
The idea behind ShadowFinder is that there used to be magic in our world, but it went away when the Gods of Old Egypt left to go a place Beyond. Then there was no magic to speak of, until a group of mystic champions arrived in Siberia during WWI to kill Rasputin, and accidentally left a few magic devices behind.
Now it’s the Modern era, and magic is common enough that most governments and many international organizations have at least one department that knows about it, and as needed deals with it. But the greatest protection a mundane creature can have is to believe magic does not exist, and so these in-the-know groups are literally protecting the world by keeping magic a secret. Further, just as vampires cannot be seen in mirror, they (and all magic effects and creatures) cannot clearly be recorded or sensed by any camera, film, or recording device, but are vulnerable to atomic weapons. So magic threats tend to try to stay out of sight, so they don’t force the whole world to grapple with their existence and potentially over-react with devastating power.
Both sides work to keep magic in the Shadows, and to find sources, allies, threats, and lost relics in those shadows to bolster their own side in a never-ending was keep just out of sight.

Classes would be drawn from various sources. Soldiers and operative from the core rulebook, certainly, with little change. Likely mechanics, but with neither drones nor exo-cortexes as common options, replaced with some other variable class feature. No solarions or vanguards at all, but maybe sword saints. Warlocks and witches seem more appropriate than mystics or technomancers, though it’d be a shame to not have some kind of modern-device-focused spellcasters — again variant classes might do the trick. Biohackers are out, witchwarpers likely in. The precog is a definite maybe, depending on how it turns out.
Weapons would scale differently, with an equipment list that didn’t assume you got higher- and higher-level weapons, but instead use weapon damage benchmarks to scale up the damage a character does as they gain levels, allowing things like pistols, shotguns, and rifles to retain utility even at extremely high levels.
In a standard characters would at least initially be part of one of the groups that monitor, track, and if needed neutralize supernatural threats, and action would primarily take place in wilderness areas, abandoned towns, lonely highways, and defunct sewers, basements, and subway lines. As players got used to how the ShadowFinder world worked, some scenes might burst into the bright light of day, only to be misconstrued by the public (and maybe even misremembered by witnesses) as gas main explosions, terrorist attacks, or herds of feral hogs.
Plots could include locking down viral zombie outbreaks before they turn into zombie apocalypses, retrieving the book that got moved to a university’s accessible library that is bring people’s nightmares to life, undead serial killers that haunt campgrounds, tracking down wererat colonies that are feeding on the homeless, rescuing student filmmakers from nighthags in the woods, capturing souls that have escaped hell, slaying evil clown demons, and racing against time to beat cultists to the artifacts of power in the bottom of dungeons built in the ancient era to prevent them from falling into mortal hands. Along the way other weirdnesses might be encounters, such as cannibalistic humanoid underground dwellers, giant alligators in the sewers, giant cockroaches mimicking humans, and genetically engineered giant spiders.
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The Gelatinous Cylinder, Part 2
Yep, more abilities for Gelatinous Cylinders, the bright red, reshaped gelatinous cube variant. Add then to the gelatinous foe of choice in your favorite d20 game.

Phantom Faces: Though gelatinous cylinders are no more intelligent than other forms of gelatinous monster, some can form a face, generally locked into one or two expressions, and repeat overheard phrases. They often repeat things said by those they consume, from prior to the victim realizing they are in trouble. This mimicry is mindless, but the sound is so perfect it cannot be distinguished form the original voices.
Tantalizingly Preserved: Gelatinous cylinders with this ability stop the passage of time for any nonliving material stuck within them, and do not dissolve items that were not living when they entered the gel. Thus they often have foodstuffs, valuables, and even high-end clothing preserved and visible, juuuuust out of reach unless you want to plunge a hand into the cylinder…
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The Gelatinous Cylinder, Part 1
Yeah, it’s themed and silly. But there are some ideas here you can apply to gelatinous foes in your d20 game of choice.
There are more abilities in Part Two.
And even more in Part Three.
The Gelatinous Cylinder
Gelatinous Cylinders are a reshaped, deeply-red-colored offshoot of gelatinous cubes. While sages agree they are magically created rather than naturally occurring mutations, and it’s generally accepted the cylinders aren’t the desired end result, there are numerous competing theories as to what the creators were trying to do.

It’s often suggested their coloration was either an attempt to make sewer-cleaning creature that was more easily spotted by repair workers, or to make gelatinous foes more frightening by seeming to be soaked in blood. The cylinder-shape is also often held up as proof these were custom-built sewer cleaners, designed to fit through pipes. Others theorize are that they were literally made to be festive and silly-looking, possibly to serve as court jesters for the Oozing Empire of sentient slimes.
Gelatinous Cylinders can have a variety of strange powers. You can emulate a gelatinous cylinder by adding one of more of these abilities to your gelatinous cube state block of choice.
Sliceable: A gelatinous cylinder with this ability takes no damage from slashing weapons. However, when a slashing attack hits it, the gelatinous cylinder has a “slice” taken off. This slice is a gelatinous cylinder one size category smaller than the original and has the same stats, but with 20% of the original’s max hit points. The original loses 10% of its max hit points each time is spawns a slice. Slices cannot themselves form slices.
Small and Innocent Looking: A gelatinous cylinder with this ability can shrink down at rest, compressing itself to Tiny size. While in this reduced form and motionless, any ability or skill check to identify it as anything more than an innocent bit of edible food takes a -15 penalty. Once touched, the gelatinous cylinder explodes out to its full size and begins attacking.
We’ll do more gelatinous cylinder abelites tomorrow and Friday!
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