Last post, I discussed issues with Five Torches Deep's fatigue, disease, and maiming systems. Today I will discuss issues with its spellcasting system.
I have played my fair share of casters in systems with unreliable casting. I had a sorcerer using Dragon Magic back in 3rd edition who risked sucking the party through a hole into the astral plane to get free metamagic. I had an arcanist in Iron Heroes who failed his roll to make the tank stronger and made him weaker instead. I had a psyker briefly in Dark Heresy before he combusted. And in the OSR space I've read, but not played, Dungeon Crawl Classics' system (for which it is well-known), and the ACKS heroic fantasy book's system (which remains obscure).
The main problem with 5TD's spellcasting is that the mishap rate is extraordinarily high.
A 1st-level caster with a +2 casting stat modifier (not unreasonable on 3d6) has a +4 total on checks to cast, and the DC to cast a 1st-level spell is 11, so they need a 7+. If they fail the roll, then they have to roll on the mishaps table, and they lose access to 1st-level spells until the next time they can safely rest (ie, between adventures).
So they're going to generate a mishap about 30% of the time. At first level the result on the mishaps table that does 1d6 damage per spell level has a 50% chance of killing (er, maiming) you. Other results on the mishap table may induce TPK depending on circumstances of casting. So you're going to want to cast very selectively.
Surely it gets better at high levels? At 9th level, your caster probably has +3 or +4 in their casting stat and +4 proficiency bonus, call it a total of +8, so now you only suffer mishaps casting 1st-level spells on a 1 or 2, so 10% of the time. Casting a 5th-level spell, though, your mishap chance remains 30%, because the DC has risen just as fast as your modifiers.
For comparison, under DCC's system, generally a failed roll to cast causes you to lose that one spell until end of adventure, and only on a natural 1 do you lose the spell and generate a mishap. Mishaps are also described per spell, so a mishap with Fireball might make a big mess but a mishap for Read Languages might be subtler and more playful. Under ACKS' unreliable casting system, mishaps are only generated on two sequential natural 1s in a row (ie, you roll a natural 1, the spell fails, you roll another d20 to see if you get a mishap, and on a natural 1 you do), but mishaps are generally quite severe (similar to rolls on the maiming table). In Lamentations of the Flame Princess, magic isn't unreliable but a lot of spells have weird or gross side effects, but never just straight-up failure-to-cast-and-horrible-mishap.
I think it is fair to say that these systems are fairly typical OSR implementations of weird and unreliable magic. 5TD's system blows them away for unreliability.
If I recall my Dark Heresy rightly, casting was rolled on a d% and you got a mishap whenever you got doubles (so 11, 22, 33, 44...). So you might successfully cast but also get a mishap in addition to the spell effects that you wanted, which was neat. But that only gives us a mishap rate of 10%, versus 5TD's 30%.
Casting a spell in 5TD is much less reliable than using psychic powers in Warhammer. Reflect on that for a moment. Is that what you want in your D&D?
The only system that compares for caster unreliability that I have seen is Iron Heroes, where one of the design goals was to make a fighter-centric game and to make wizards bad.
I think the best archetype ability in the game might be the wizard's ability to reroll mishaps. The cleric's ability that gives allies advantage on rolls on the maiming table is sort of ridiculous (and here I thought a 1-in-20 chance of death was too low; 1-in-400 is just comical), and the fighter's action economy thing that lets you turn a move action into a standard action for an ally is also strong (strong party comp: one cleric with Reforge and advantage on injury rolls and then a pile of fighters who can turn move actions into standard actions for allies, and who use it on each other to give extra full attacks once you can make multiple attacks with a standard action, every round because the rules don't say how often you can use it). But those are gravy abilities, while rerolling mishaps means that you can do the main thing that your class is supposed to do and you might not even kill everyone.
It would be one thing if 5TD's spells were wildly good, so you were taking a big risk in hope of a big payoff. But I don't see that here. Sleep scales up better in terms of hit-die limit than it does in OSR games so it probably remains viable across the level range, but you have to roll to hit with it now and I don't think the HD limit is high enough that it will ever be a straight-up encounter-win. Magic Missile scales up a bit faster than usual but again there's a to-hit roll now. Fireball looks bog standard. A lot of spells now require Concentration in 5TD that don't normally. The healing spells look stronger than I'm used to, and there are a few other stand-outs on the divine list, but overall most of these spells don't look as punchy as their OSR equivalents, for the level when they become available.
Back in third edition, we had a rule of thumb that any spell that required an attack roll and also gave that target a saving throw needed to have a really big effect, because it was probably only going to work a quarter of the time. Phantasmal Killer followed the same logic - save or die as a 4th level spell was OK because it required the target to fail two saves based on different ability scores, which meant in practice that it almost never worked. The same is true here - any spell in 5TD that requires an attack roll needs to be really punchy, because it's going to fail (and blow up in your face) a third of the time on the roll to cast and then half the time on AC.
Quick / minimal fix: spellcasting only generates mishaps on a natural 1. Failing to cast a spell causes you to lose that spell until your next safe rest, not all spells of that spell level.
I'm not really sure this is enough to save 5TD's spellcasters. They also have to deal with spell components, at a rate of two Supply worth of components per spell level. So even under the default system, an 18-Int wizard can only carry 9 spell levels worth of components. That sounds like a lot at 1st level, but even if you're pouring your stat increases into Int you're only getting 21 at 9th level which doesn't go very far with 3rd-5th level spells. And that's starting with 18 Int! If you're playing an Elf, your 13 Int gets you six levels of spell components, and if you put all your points in Int you'll get nine levels of spells at 9th level. And may the gods help clerics with low Int, who still need the same amount of supply in spell components.
There is a note about "focuses", orbs and staves which obviate the need for spell components entirely. But as there are no treasure tables, distributing these is left purely to DM fiat.
Quick fix: make spell components 1 SUP per spell level. This is a band-aid.
It isn't 100% clear to me whether components are consumed on a failed spellcasting check, but that would be a worthwhile clarification to add.
Anyway, as far as I can tell this spellcasting system is dramatically worse than anything I've seen in the OSR.
Next, last post in this series: the critical thing that 5TD misses about OSR play.