Wednesday, June 20, 2012

Hit points as spell points

Wandering from blog to blog a few days ago, I stumbled upon a free download of a fantasy RPG called Errant.  Reading through it, the feel I got was very similar to that of D&D, with some notable differences.  One of the interesting mechanics was using hit points as spell points, with casting cost of 1 hp per spell level.

This models quite well the fictional portrayal of spell casting as a physically exhausting endeavor.  There are some aspects of it that I really like, and some that I'm not so sure about with regards to porting it over to a more traditional D&D framework.

The positives

It maintains the resource management aspect of spell casting, without the rigidity of a table of spells per level per day.

The bookkeeping is minimal.  In fact, it eliminates a whole category of bookkeeping in the game.  You already have to keep track of hit points anyway, so it adds virtually nothing to overall complexity.

It would technically give low level magic-users the potential for casting more spells than the traditional Vancian tables allow, but at the same time it provides a very strong incentive to stay well below that limit most of the time. 

It provides the potential for epic sacrifices and desperate ploys, as a mage burns his last hit points on a spell to save the day.

It strengthens the incentive for magic-users to stay out of the front lines of combat.

It provides for interesting tactical choices for a worn-down party:  Do the healers refresh the fighters, or recharge the mages?

You can adjust the lethality of overreaching one's capacity according to your own preference.  Dropping to zero hp from spell casting might result in death, unconsciousness, or a saving throw with success indicating unconsciousness and failure death.

The not-so-positives

It obviously won't work for clerics, or for any class that can cast healing spells.  Even barring a caster from casting such spells on himself isn't an effective control.  Put two healers in a party, and you've got a perpetual casting machine.

Casters with high Constitution scores are strongly favored.  In fact, Constitution becomes more important to a magic-user than Intelligence.  Errant keeps Intelligence relevant by requiring an ability check to successfully cast the spell in the first place, but I think that overcompensates and ends up overemphasizing a high Intelligence score.  Perhaps using Intelligence as a chance to learn a spell, and/or a cap on number of spells known, would strike a better balance.  A high-Con character would have an early advantage, but the high-Int character becomes far more versatile in the long run.  Of course, it's possible to have a magic-user who's both, but 3d6 in order makes that unlikely.

Classic D&D elves are a problem, because they have more hp than a magic-user, and thus a greater pool of spell points.  This might be mitigated by charging an extra point per spell level, or even doubling the cost, for elves (and other multi-class magic-users, in an AD&D-style game.)

Hit points vs. Vancian slots

Here's a side-by-side comparison showing the number of spell levels available to Vancian magic-users of selected levels vs. the average number of hit points.  (Mentzer rule set)

Level          Vancian spell levels total          Average hit points (rounded up)
1                  1                                            3
2                  2                                            5
3                  4                                            8
4                  6                                           10
5                  9                                           13
7                 17                                          18
8                 23                                          20
9                 31                                          23
14               67                                          28
21             141                                          35
36             405                                          50

Hmmm...that's great for low-level magic-users, but it quickly becomes a substantial handicap at higher levels.  It turns out that magic-users gain spell slots a lot faster than they gain hit points, and above name level, it's one paltry hit point (i.e. one measly spell level in an hp-as-sp system) per level.  A 36th level magic-user in the original rules can cast nine spells of each level per day; with the hit point system, he's running on fumes after casting only one of each level.  Granted, he's gaining something in versatility, being able to choose whatever spell fits his needs a the moment, but at what a price!

Maybe it's not as bad as it seems.  In the spell slot system, a caster has to memorize spells in advance, and either correctly anticipate which ones he'll need, or choose a broad selection, with a lot of them likely going unused on any given adventuring day.  In the hp system, if he needs five Knock spells, he has access to them, and doesn't have to anticipate the need for them or load up his brain with a lot of superfluous stuff.  In other words, most of the time, just because a magic-user can memorize a lot more spell levels than a hp-fueled magic-user can cast, it doesn't follow that the Vancian wizard is necessarily going to cast a lot more of them.   Combined with the fact that healing magic actually restores the hp wizard's reservoir of spell power, it might actually be pretty close to a wash.

If all else fails, perhaps (if I may steal a mechanic from another source) magic-users should be allowed a saving throw vs. spells to avoid the hp drain, with a penalty equal to the level of the spell being cast.  Low level casters would still lose hp on most casts, while high level ones would feel the drain less often. 

Even if I decide that extra roll is needed to keep things close to the original balance of power, it still might be worth it not to have to do all the accounting for spell slots and memorization.  Painstaking selection of an extensive list of spells every morning of game time (and for every NPC magic-user,) or roll a single die once and subtract hp or not each time a spell is cast...that sounds like a fair trade.

Despite my misgivings about the possibly excessive gimping of high level magic-users, and my fondness for my recently posited spell component-based system, I think this just might be the way to go for my group, which includes my young nieces whom I very much doubt have the patience for a lot of bookkeeping.  Now I just need to find a similarly elegant mechanic for cleric spells, to avoid the healing conundrum (and in the process, maybe even provide a really substantive difference from arcane spell casting other than just different spell lists.)


  1. I actually don't mind decreasing the number of spells that high level wizards can cast. I have always found it a bit awkward to track, and it's kind of odd how spell casters continue to gain so much firepower per level while other classes don't. And as you note, picking all those spells to prepare is a lot of work. And, wizards also presumably acquire or make magic items which give them even more options. I think the traditional D&D wizard would probably work just fine with no added spell slots after either 9th (name) level or 14th level (the end of B/X).

    A few other minor points:

    - You could give wizards (or even all classes) bonus HP for their prime requisite rather than constitution, given that HP are abstract anyways.

    - You could track the spell point pool separately from HP, but give it the same max (this avoids the healing magic battery problem and doesn't really add much complexity). 0 spell points could still result in unconsciousness from exhaustion (or just call it non-lethal damage).

    If I didn't do something like the second option, I would seriously consider removing easily available healing magic altogether, because otherwise HP = mana will lose its flavor, I think.

    You also might want to check out the discussion at this post:

    1. Yep, there's that old "linear fighters vs. quadratic wizards" thing. The more I think about it, the more I agree with you that drastically slowing down spell progression isn't such a bad thing.

  2. One reason I do like the Vancian 'fire-and-forget' system is that it forces players to anticipate the obstacles they might encounter. They have to do a little thinking and a little planning. And when they get it wrong, then they need to find creative ways to use the spells they have memorized. I'd just flatten out the power curve a bit, giving a low level caster a few more spells and a high level caster a few less spells.

    However, for other HP spell casting systems, you may want to check out Microlite 20 or Akratic Wizardry's house rules (here:

    1. I'm not really a fan of trying to anticipate challenges to choose spells. More often than not in my experience, the result is a stock list of "safe" spells, and the niche spells are rarely chosen. There's a certain monotony to it, a lack of the spontaneity and free-wheeling problem solving that I associate in my mind with magic. It doesn't feel like what I want magic to feel like. I realize that's a matter of style, though, not "this way sucks but that way doesn't."

      Akratic Wizardry's rules look pretty similar to what I had in mind, but with even higher hp costs. That actually makes me feel a little better about paring off so much power from higher level casters, because he's gone even farther, apparently without serious issues.

    2. He also gives a D6 hit dice for magicians, which balances things out nicely.

  3. Here's another crazy idea I just had that might work well in concert with this: every point of magical healing causes one day of aging (the natural healing rate being 1 HP per day; adjust as desired). This would not affect any particular instance of spell casting very much, but if magical healing is used frequently, characters will grow old before their time. It would also explain why healing magic does not change society drastically.

    1. That makes a tremendous amount of sense, actually.

      I'm also considering tracking spell fatigue damage separately from physical damage, much like I used to do with lethal and non-lethal damage. (No need to do that any more, since I decided that all that matters is the blow that reduces you to zero. If it's a sword you die, and if it's a punch, you're down for the count.) Magical healing could restore spell fatigue, but at a rate of 1 hp per spell level instead of the healing spell's usual range. That would make it a wash, but still marginally useful if you've got a fatigued magic-user getting a slight recharge from a fresh cleric.

  4. I found myself here via Brendans blog. I'll repeat what I wrote there.

    "I use hitpoints as spellpoints as per Akrasia's rules. They solve the problem by dividing hitpoints into hitpoints and real wounds. Healing heals wounds, but not hitpoints. Hitpoints also regenerate fully after a nights rest, but the real wounds heal slowly.

    I really like the emergent properties this system has with magician characters. They can have D6 hit dice, but they still avoid combat like the plague. My elves are good at both fighting and magic, but have a D4 for hit dice. :)

    The downside is that the characters need to rest more often."

  5. You might be interested in this post over at 1d30, it may offer some solutions to the healing problem.

    The first alternative is the one to look at (the others would likely make the problem worse) - every time you're healed magically, you might get screwed up in the process, and your max hit points go down.

    I'd probably ramp it up from what is proposed over at 1d30, and just say that you DO lose one HP from your maximum every time you receive magical healing, with a chance to lose more.