YAOSC: Time to build some magic


Recently I’ve been putting renewed thought into my fantasy heartbreaker RPG; in this case, the long-deferred question of how the magic system will actually work.

My Magic Monday series has ended up as a sort of catch-all for fantasy RPG stuff, including the God-eaters campaign outline, but its backbone is built of over sixty posts detailing magic spells based on my “Four Realms” setting and intended for use with YAOSC. These posts show a lot about the assumptions I was making about how magic would work:

  • Most spells are versatile but require planning and preparation to use effectively – or at all, in some cases.
  • Each spell’s power, difficulty, and resource cost could be balanced against each other depending on the caster’s needs or situation.
  • Magic has a major role in world-building, and most spells are intended to suggest either real-world “pragmatic” magical traditions or a mythic, fairy-tale feel. Magic is not designed to be used for direct harm as in D&D-style tactical combat.
  • Magic is available in a variety of forms, including rituals (time-consuming activities that can be powered by groups of participants), rotes (common “spell magic” as TTRPGs tend to use it), and gnosis (effects achieved through willpower alone).
  • Magic is cast through a normal skill check, adding together the caster’s scores in the Rote spellcasting skill and in the Spell Specialization skill for that spell (if they have it).
  • Spell-magic would be limited to trained magicians; everyone else would use items or participate in rituals.
  • The primary resource would be mental strain, with options to substitute fatigue or even hit points in limited situations.

After thinking things over for a while, I’ve decided to change the last two points.


I like the idea of almost any character potentially having access to a little magic. Previously, my working skill list had marked both Rote and Spell Specialization as off-limits to everyone but sorcerers, but now I’ve changed that to them being difficult skills (i.e. costing more skill points to buy) for warriors and priests. For the specialist class, Rote itself is difficult, but Spell Specialization is normal. These values might be tweaked again after more thought or maybe some playtesting, but for now it feels good.

The expected result is that a few characters will pick up a spell or two just to have a trick up their sleeve – and that specialists will have slightly broader options than other non-sorcerers – but that the bulk of magic will still be the province of dedicated magic-users. After all, after a certain level of investment, you might as well save yourself a load of skill points by being a sorcerer.

The more fundamental change that I want to make is to the resource cost. With strain alone being the primary fuel for magic, I felt enormous pressure to add in a bunch of kludges that would expand the number of points available for spellcasting, including roping in other skills to help grow and replenish the resource pool.

What I’ve landed on instead is two changes. First, any of the resilience meters can be used to power spells, as the caster decides. (For a handful of spells, a cost specifically taken from one of health, endurance, or mental stability feels thematically appropriate, but those will be the exceptions rather than a confusing standard.) And second, I want to standardize a number of tools that can be plugged into the power/cost/difficulty balance.

  • Every spell has a base cost, difficulty, and effect. Let’s set “effect” aside for the time being.
  • Unless otherwise noted, increasing the difficulty by a step will halve the cost (or vice-versa). Let’s say that fractions get rounded down, so a cost of 3 could be “halved” to 1 and then to 0 through a two-step difficulty increase.
  • Standard wizard tools will include items that decrease the difficulty of spellcasting, usually by one step.

This means that we can set the base cost and difficulty (for a given standard effect) according to how we want to see that spell used in the game. I came up with a list of questions that can be used in making those decisions:

  1. How often can an unaided first-level magician successfully cast the spell?
  2. At what level can casting become automatic? (i.e. the skill score surpasses the difficulty)
  3. At what level can casting become free / unlimited (i.e. the cost can be pushed to zero)?
  4. What can a specialist with specialized tools (a min-maxer) accomplish?

Mathemagic: resource cost

At first I was going to include the question “Will this spell be possible at all for a first-level magician?”, but in YAOSC there’s essentially always a chance of success. Even if you only have one point and are facing a d100 difficulty, that’s still a 1% chance of pulling it off. And while a challenge roll technically becomes impossible sooner or later, the (1%) chance of a roll of 21 (from 2d10+1) against an opponent’s roll means they’d need to have a score of at least 20 to automatically defeat you.

Assuming a system where some skills have a bonus from ability modifiers and where skill point investment is limited to one per level, we can guess that a first-level sorcerer will have one point each in Rote and the relevant spell, plus one point from a decent Intellect score, for an unaided score of 3.

Let’s assume that this first-level sorcerer is (wisely) unwilling to dip into HP as a spellcasting resource, or to zero out their other meters, outside of dire emergencies. Based on this character-creation outline, their starting EP are going to average in at 7, and SP at 3, giving a pool of up to 8 points that could be spent on a spell.

In other words, even a completely unaided (average) sorcerer can be expected to cast one of their trained spells more often than not (75% rate) at a d4 difficulty, and 50% of the time at a d6 difficulty. And they can double any casting cost of 4 or less to make the d6 spell a d4, with a 75% chance of succeeding, or make the d4 spell into an automatic success.

The minimum possible survival meter values at first level are 2 EP and 3 SP, for four usable points; the maxima are 14 EP and 6 SP, for eighteen usable points! That’s a lot of swinginess and it kind of makes me want to rethink the starting meter values, but for now we’ll say that if you want a spell to have guaranteed accessibility, it should top out at a cost of 4. On the other hand, a spell would have to have an abnormally high cost (at least 15) for that consideration alone to put it out of reach of even a first-level magician.

Mathemagic: to difficulties, and beyond!

Setting that aside to look at difficulty, let’s assume a base cost of 3 for a spell. This requires two steps of increased difficulty to completely ameliorate the cost and allow for unlimited casting; a base d3 difficulty would become d6, allowing even odds of success for a first-level caster. A standard base difficulty of d6 would become d10, for a 30% chance of success at casting the spell for free.

This sounds like it should be pretty meaningless, given that you have infinite zero-cost attempts and can theoretically just try over and over until you hit that 30% probability. The obvious solution is to plug in a spell-failure chart: if the first degree of failure carries a nonzero energy cost, then you avoid the “infinite retries” issue. And if each degree of failure beyond the first (i.e. every five points by which the roll was missed) imposes an even worse consequence, then a score of 3 on a d10 will give you not just a moderate chance of spending energy to no effect, but you’ll also have the exact same chance of some sort of arcane catastrophe as you do of succeeding. In other words, a spell-failure system transforms long odds from a boring numbers game into a gamble, to be reserved for desperate situations. That sounds good.

This number-tinkering has given me an idea of the shape of the power curve as well. Early levels will see a lot of influence over any skill-based roll from talent (ability score modifiers), luck (the dice themselves), and circumstances. All the more so for characters without ability bonuses who try to wing an untrained spell using only one point of Rote: with a mere score of 1, even a minimal d3 difficulty becomes a bit of a risk.

But over time, talent and luck will be overwhelmed by character skill and resources, and circumstances will be overcome at least in part by player strategy. At level 10, a magician casting a spell they’ve specialized in can expect to have at least 23 points: +1 from ability, +2 from tools, and +10 each from Rote and Spell Specialization. A score of 23 means that a d20 difficulty (something that a first-level magician would likely only risk when death was on the line) is an automatic success, and a d30 difficulty gives very good odds, especially if the caster is able to tinker with the casting time or pump in extra energy. In other words, YAOSC is a system where level 1 characters are normal humans, and level 10 characters are legendary heroes or demigods.

That seems like a good amount of theorizing for one post, so we’ll wrap things up here. What we’ve found is that:

  • Difficulties of d3 and d4 aren’t meaningless. They still present some risk to non-specialists, especially at low caster levels. On that note, it’s perfectly fine to open up magic to non-sorcerers without running afoul of “niche protection” issues, because getting really good at magic will consume a huge number of skill points.
  • Smallish resource pools aren’t a problem, in part because a dedicated sorcerer will be able to cast their signature spells for free soon enough.
  • A base difficulty of d6 and base cost of 3 are reasonable benchmarks for scaling spell power levels.
  • It’ll be necessary to impose some sort of cost on spell failure, if only to keep players from abusing a “roll ‘til you make it” strategy with cost-free spells.
  • It’s okay for spells to ask a lot when pushed to high levels of performance; a high-level character can face down d30 difficulties in their specialty without batting an eye.
  • By around 10th level, play will be shifting from a human to a mythic or cosmic scale.

And the best part is that these conclusions will also inform how all the other skill fields (outside of magic) should be balanced and structured. We’ll see how that looks.

About Confanity

I love the written word more than anything else I've had the chance to work with. I'm back in the States from Japan for grad school, but still studying Japanese with the hope of becoming a translator -- or writer, or even teacher -- as long as it's something language-related.
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