Overcasting - which systems have this?

[Altair_the_Vexed]

A common trope in fantasy is that some magic is too powerful for the inexperienced dabbler, and that getting it wrong has terrible consequences.

You know the sort of thing: get the spell wrong, and you've summoned your intended devil, but not contained it properly... Or you've scried on your target, but cursed yourself to see visions of the horrors inside everyone you meet... Or your cleaning spell drowns everyone in a 3 mile radius...

In the same fiction, you can often cast less tricky spells routinely, without fear.

On the other hand most RPGs I know of that even bother with some sort of skill check for magic have no dire consequences, just failure (of course, failing to get your spell off when it counts can have its own dire consequences!)
In most RPGs, you can't even attempt to cast beyond your current power. When you gain access to a spell, you can use it reliably.

So before I go making my own homebrew, can you lovely folk point me to any game systems that have done this sort of thing before?

(I'm not asking for a debate about whether it's a good idea - although comments on how successful any system you've encountered is will be welcome.)
(Also, I should say I'm familiar with the various D&D editions' wild magic systems. Not really what I'm after, as they're usually a bit silly and jokey.)

[Anonymouswizard]

I've seen several systems which use a 'you can burn HP to make up for missing MP' mechanic, some of them as standard and some as learnt abilities.

In terms of 'dangerous failed castings' I can't really think of anything. Failed spells in the various Warhammer games can cause daemons to eat everybody's souls, but so can successful spellcasting rolls.

[Hellpyre]

In terms of 'dangerous failed castings' I can't really think of anything. Failed spells in the various Warhammer games can cause daemons to eat everybody's souls, but so can successful spellcasting rolls.

I was going to say Dark Heresy, but really, you're right. Routine psyker abilities by no means equal safe - just relatively less likely to kill everyone.

[malachi]

It also doesn't really fit your request, but Iron Kingdoms Full Metal Fantasy RPG allows typical spellcasters to 'push beyond their limits'. Every caster has an ARC stat, and that tells them how much magical power they recover every turn. They can cast up to twice that much in a turn, but if they cast more than their ARC stat's worth of magic, they fatigue themselves (which simply ends their current turn after the spell is cast, and means they can't cast anything next turn).

So, that's something to consider as an aspect for homebrew, but sadly not what you're looking for.

[Altair_the_Vexed]

Thanks so far - Warhammer's casting systems have always had that grimdark aspect, so that might be worth looking up.

Burn out is something I'd not thought of tying into the whole idea, but maybe it works. Tired people make more mistakes...

[Anxe]

The "push yourself" and "Devil's Bargain" options from Blades in the Dark fit pretty well with going beyond your normal power. But there aren't any real spells that are defined in that system.

[Telok]

Dungeons the Dragoning does it pretty well. The game is a hideous mash up of d&d, wh40k, vampire & werewolf, exalted, and at least one other system. For a 4chan April Fools joke it is surprisingly playable and fun.

Casting as follows:
Roll spell school skill + associated stat d10s. Keep stat, explode on 10s.
Each spell has a target number, make the number and the spell works. Some spells get better as you beat the TN by more.
You have the option to overcast by adding dice to the number of dice rolled.
If you kept any 10+ dice or overcast roll % on the perils of the warp table. You add % to the roll per 10+ die or overcast die.
The perils table is 1 to 75 of nuisance, mild danger, or just dramatic special effects. A 76+ roll kicks you up to the warp phenomina table where the nasty stuff lives.

Casters can 1/2 rolled dice to cast 'fettered' which is always safe, no matter how many 10s get rolled. Fettered casting is always safe.

Sanctioned casters can overcast by up to 3 dice. For each kept 10+ die and each overcast die they add 5% to the perils roll.

Unsanctioned can overcast by 4 dice but their perils are at +10% per die overcast or 10+.

Getting sanctioned is taking a feat and a little rp.

[Psyren]

D&D/PF does this, not through regular casting, but via Rituals/Incantations. If you're angling for a low-magic setting where powerful effects are locked behind a casting system that incurs risk or drawbacks, this might be the way to go.

You can also layer danger and negative consequences into the more traditional magic system by introducing elements like Taint or Spellblights.

[weckar]

I think the original Dresden Files RPG had traces of this. I never quite wrapped my head around it while we played it, but our resident caster certainly dealt with it on occasion.

Less known, more familiar to me: Tri-Stat handles this beautifully. In fact, if in that system you do this enough times successfully, it actually increases your power.

[Anonymouswizard]

I was going to say Dark Heresy, but really, you're right. Routine psyker abilities by no means equal safe - just relatively less likely to kill everyone.

To be honest, it works for the Warhamer games, you're kind of not really supposed to play a Psyker/Wizard because they're rare and dangerous, but sometimes it's appropriate.

As a side note, I've been considering adding magical phenomena to D&D/Pathfinder/Starfinder. After casting a spell you'd rol a d10 and getting equal to or lower than the spell level would cause you toll on a table (maybe d&, maybe 2d10) with a number of minor effects, such as making the surrounding area hotter/colder or generating smells and sensations. But I'm thinking of just replacing it with every character having a unique 'mark' for their magic, one character might chill their space by a couple of Kelvin per spell while another creates the smell of chestnuts.

[Morty]

Dark Heresy does have "pushing", where you invest more into a power while increasing the risk of mishaps. The reward isn't worth the risk, though, at least in the second edition. Never played the first. Wrath & Glory has something similar, not sure how it works out in practice. Though in general, I'm not fond of WH40K RPGs' binary of "nothing happens" and "random mess happens", especially since the phenomena can be something harmless or really bad, once again entirely at random.

I believe Mage: the Awakening 2E has a "reach" mechanic where a mage can risk more Paradox for increased power, but I've never been interested in M:tA so there's not much I can say.

[Grod_The_Giant]

I think Lamentations of the Flame Princess has something along those lines? It's a dark fantasy D&D retroclone; I had a friend in college who talked about it a lot.

[martixy]

D&D/PF does this, not through regular casting, but via Rituals/Incantations. If you're angling for a low-magic setting where powerful effects are locked behind a casting system that incurs risk or drawbacks, this might be the way to go.

You can also layer danger and negative consequences into the more traditional magic system by introducing elements like Taint or Spellblights.

Another few flavours:
3.5 Psionics has Overchanneling
PF has "Overclocked spells"(what a silly name, this is not a computer) in PF Unchained.

[Tanarii]

Forbidden Lands has levels of spells, and you learn with a Talent Rank 1, Rank 2, and Rank 3. When you start a caster you typically know Rank 1, maybe Rank 2 if you focus the character.

If you cast at your Rank, you roll dice equal to the Willpower spent, and base power level is equal to WP spent. Each die has a 1 in 6 chance of overpowering (it counts as +1 PL, effectively doubling that WP value), and a 1 in 6 of a magical mishap (one mishap max per spell). Usually you're either spending 1 WP or 2-4 and more seriously chancing a mishap.

Safe Casting: If you cast a spell of level lower than your rank, you can pass on one die per difference, which means 1 less die for casting a Spell Rank 1 at Talent Rank 2, or up to two less at Rank 2. That reduces the chance of a mishap, but also of overpowering.

Chance Casting: casting one higher spell rank than your talent rank always triggers a mishap. (Which means you might as well dump a bunch of WP into it to boot!)

Mishaps top out at 1 in 36 chance of a demon popping out and perma-stealing your character before anyone can react. Also includes same chance of accidental demon summoning, plus various self-inflicted critical hits (serious), and a lot of 1 pt of ability damage (that's light to moderate damage depending on your character and the stat).

[Seerow]

Shadowrun uses drain as it's primary resource limitation for magic. Basically any spell can be cast at a force rating equal to your magic stat. The damage gets resisted by your willpower. So weaker spells can be cast more or less at will, while stronger spells inflict drain, which is basically nonlethal damage that can't be healed except through natural rest. More powerful wizards have better willpower and focii to help negate drain so can cast stronger spells more freely.

It's been a while, but I think you also had the option to cast at a force over your magic stat, but take lethal drain instead of non lethal. That may be faulty memory or a metamagic option.

[Ignimortis]

Shadowrun uses drain as it's primary resource limitation for magic. Basically any spell can be cast at a force rating equal to your magic stat. The damage gets resisted by your willpower. So weaker spells can be cast more or less at will, while stronger spells inflict drain, which is basically nonlethal damage that can't be healed except through natural rest. More powerful wizards have better willpower and foci to help negate drain so can cast stronger spells more freely.

It's been a while, but I think you also had the option to cast at a force over your magic stat, but take lethal drain instead of non lethal. That may be faulty memory or a metamagic option.

There is such an option, and it's literally known as overcasting. You can cast spells of Force up to twice your Magic, but if it's higher than your Magic, you take lethal (Physical) damage.

[NichG]

Slayers d20 (and 'Advanced d20 Magic') are adaptations of D&D 3.5 where basically anyone - including characters without a casting class - can in principle attempt to cast a spell of any level or school. Learning the spell requires open slots (and non-casters don't have many of these, so you can be a commoner with a single signature 9th level spell, but you're not going to have the diversity of a wizard) and a skill check against a DC based on the spell level and any components it would normally entail (for reference, 3rd level spells are generally about a DC 30, 9th level are around 55, but Wish is 101 because of the XP component). Having a tutor, using a library, having caster class levels, etc all provide substantial bonuses to this skill check, but it doesn't strictly rule out a 1st level commoner with temporary access to a skill boosting item and some friends buffing them from learning Gate, though it would take some doing.

Once you've learned the spell, casting it requires two checks - a Fortitude save against the spell DC, and something called a 'Control check' which is basically a stat mod + levels in casting classes check. If you pass the Fortitude save, you don't need to make the control check - you take non-lethal drain based on the spell's DC, and the spell goes off. If you fail the Fortitude save, you take double drain and have to make the Control check (at which point iirc the spell could fail outright if you're way below, go partially out of control if you're within 10 but still fail, or proceed normally if you pass the check). However, you can also up the stakes if you really want that spell to work - doing things like adding material, somatic, sacrifice, etc components to the spell gives a bonus.

So you could, at least in theory, have a Lv1 commoner learn Wish, spend a decade preparing an elaborate ritual that involves sacrificing the souls of everyone in their hometown, attempt to cast it, kill themselves from drain, but have the spell work but go out of control creating weird effects in the vicinity.

Though, do keep in mind that this is a system which said 'y'know, casters in D&D are just too weak to represent our source material...'

[Anxe]

I just remembered that Hackmaster also has overcasting rules. Pumping more spell points into a spell increases the chances of a spell mishap and the severity of the spell mishap.

[caden_varn]

The original Torg game had a similar mechanic to Shadowrun. You have two target numbers - a lower one you need to meet for the spell to work, and a higher one to avoid backlash damage. Sadly IMO, they removed this from the new game. The new one makes magic, miracles & psionics use exactly the same system which I think is a shame - the little differences between them made them feel distinct, now it really feels pretty homogeneous.

[Glorthindel]

To be honest, it works for the Warhamer games, you're kind of not really supposed to play a Psyker/Wizard because they're rare and dangerous, but sometimes it's appropriate.

The first character who died in my Dark heresy campaign was the Psyker. It was a pitched battle between the party and a group of four Witches, with Psychic abilities flying unrestrained on both sides, and multiple unexpected phenomena. Then when the fight had ended, and all the effects that increased the danger of casting had subsided, the Psyker used a lowest-tier healing ability on the badly wounded sniper, and got himself sucked screaming into the void. Some days in Warhammer/40k even the simplest spells mean catastrophy.

[Psikerlord]

2e Shadowrun had overcasting, not sure on later editions I cant remember. I dont think 5th has it.

Low Fantasy Gaming has a table of "Dark & Dangerous" magic effects that can trigger when using magic (starts at 1 in 20, then increase by 1 every magic use until it triggers. There are no cantrips/at will magic in the game).

[Komatik]

I don't remember all the specifics, but The Riddle of Steel has spellcasters rolling against the drain of magic - permanent aging - with every spell cast. Casting easy spells lets you use more dice to resist the drain, putting it all in power will leave you defenseless and failure to resist can just knock you out if you age too much at once. The faster you cast a spell, the more difficult it is. If you cast a spell more slowly than you have to, you can marshal more dice to use for power (to ensure success) and safety.

[Lord Torath]

Dragon Kings (2E AD&D Dark Sun sourcebook) had sensory effects for casting spells, with more powerful spells getting more noticeable effects. There were visual effects (slight glow around the caster's hands), audible effects (angelic choir, chimes, low growl) olfactory effects (smell of cinnamon, swamp, or wet dog), taste effects (roast chicken, armpit) and tactile effects (everyone feels hundreds of tiny feet running up their spine), and the higher level spells had larger radius of effects and a greater number of effects. Really powerful magic could summon strong winds or dark clouds over the caster's head for the duration of the casting. In a world were wizards are outlawed...

[JeenLeen]

So before I go making my own homebrew, can you lovely folk point me to any game systems that have done this sort of thing before?

(I'm not asking for a debate about whether it's a good idea - although comments on how successful any system you've encountered is will be welcome.)

I think I've seen it in some systems, but I've never seen it done well. Maybe you could look at the corruption mechanics in the horror splatbook in D&D 3.5 (Heroes of Horror?). I think some spells could give corruption, which would eventually give penalties.

As something to think of if you homebrew, I think the biggest issue is finding a balance between two extremes. Usually a mechanic like this (or corruption/taint mechanics) fails because either
1) the penalties are so bad that it's never worth doing (except maybe in face of death/TPK, and even then you might not want that PC afterwards), so the mechanic might as well not exist
OR
2) the penalties are so minor or can be mitigated mechanically by appropriate actions or mechanically-savvy players, so the risk element is effectively removed and the mechanic might as well just be a risk-free power

Both extremes tend to reward mechanics knowledge and penalize new players, as (for #1) new players might not realize it's a trap and ruins their character or (for #2) only savvy players realize how to avoid the penalties and use it risk-free.

A good balance where it is an option, but only when needed, is hard. I think you'd want something where the penalties are temporary (so you don't permanently mar your character), but they also can't be mitigated by the party just saying "well, we rest for a week". I've talked some possible solutions with other game-design hobbyists before, but never found something really satisfactory. Something did just occur to me as a "narrative time" element, in that you are 'cursed' with whatever penalty for a certain narrative time span, that is, X game events. So even a year of downtime doesn't remove it. Justification: 'because magic' (or hopefully something internally consistent with the metaphysics of your world.)

In that sense, I found the Paradox system of oWoD Mage relatively sound. It was fairly arbitrary to the DM to assign penalties, and you could wait it out if there was no in-game reason to rush to the next plot point, but it seemed to balance "well, you can do this, and should do it sometimes, but do it too much and BOOM, or you turn into a newt, or, y'know, something bad".

[DeTess]

2e Shadowrun had overcasting, not sure on later editions I cant remember. I dont think 5th has it.

5th has it, pretty much as described above (Spells can be cast at a force equal to up to 2*magic stat, but if you cast your spells at a higher force than your magic stat, you take drain as lethal damage, instead of nonlethal).

[tomandtish]

Green Ronin's "Black Company" setting has this. ALL magic use requires a spell-craft check, which gets harder the more you put into it.

[Duff]

I'm having an Ars Magica day today - Normal Ars Magica has the risk of twilight (indeed, if your game goes long enough, a spell botch is probably what will end your career).
But there's also an optional merit which lets you throw life points into your casting. If you roll low enough that you need all your life points, you die

[paddyfool]

Fantasy Craft has options for this, although the default option simply makes it harder to cast further spells if you botch a difficult one.