Using hit points to power magic

[PeterFitz]

OK, here's my initial plan for hit-point costs for spell-use.

To cast any spell, it costs you (1d6 + spell level) points, which comes off your maximum hit-point total.

Note that point: off your MAXIMUM hit point total. That means that magic use may actually cost you hit-points, but more importantly, it will affect the amount to which you can be cured.

Example: you have 50 hit-points, and you cast three level 3 spells which ends up costing you a total of 20 points. That means that you now effectively have only 30 hit-points. Just like physical damage and fatigue. The difference is that if you then take another 10 points in a fight, and get some magical healing or use one or more of your healing dice, you can't heal up past 30 points — your new Hit-Point Maximum. If you use more magic, your Hit-Point Maximum will drop still further.

Note that if you've taken 10 points of normal damage (to 40hp) and then cast a spell that drops your Hit-Point Maximum to 45hp, you won't immediately lose any more hit-points. It just means that you can't be healed up to your usual 50hp.

If you then cast another spell that drops your Hit-Point Maximum to 39, you'd actually lose that hit-point, because your new Hit-Point Maximum is lower than your current hit-point total.
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A spell that requires Concentration to maintain will have to be paid for again if circumstances require a Concentration check (though it doesn't require new verbal, somatic or material components to be expended). If the check fails, you won't lose any hit-points, but of course the spell effect stops.

A Long Rest will return your Hit-Point Maximum back to normal, but nothing else will (unless you have a spell or magic item or something that will do it — see below).

It's not all bad news though. I'm doing away with spell slots — I think the hit-point cost is limitation enough. (Note that this will be subject to review after proper play-testing).

I'll also be designing some magic items that can be used as hit-point sinks (i.e. that can be used to power spells before you have to use up your own precious life force) — probably along the lines of ioun stones and the like — some of which can be recharged, others of which will be disposable items.

 

[GreenTengu]

1d6+ spell level is way too expensive for 1st level spells and way, way to cheap for 9th level spells.

Think about it-- it means casting a basic 1st level spell at 1st level could very possibly cost more hit points than a character has.... meanwhile a 9th level spell will only cost a maximum of 15 hit points which is literally nothing for those high enough level to use them (assuming you are still gating the level from which they can use certain level spells).

Your idea is not horrendous in concept, it is a matter of trying to find the balance and also figuring out what happens if you reduce your maximum possible hit points below 0. Because that is definitely going to happen to low level characters a LOT under this system for them to just cast the same amount of spells they used to be able to cast normally.

A better cost might be 2 hit points per level of spell, but the higher level spells still seem way too cheap.

If you think about it, spells basically equate to getting to either restore or cause about 1d8 hit points per level of spell, but with higher level spells being able to pack that whole punch into a single round is hugely more beneficial than doling it out one round at a time. So maybe a better system would be

2->3->4->6->10->15->22->34->51

Or something like that... basically each level costs you more and more and more in order to use it. And you might still cap over 7th level and over as once per a day.

 

[PeterFitz]

You make a good point — I shall have to do some calculations.

Something else that was suggested is the advantage that high-hit-point casters (e.g. clerics) would have. That could be balanced, I think, by focusing the creation of magical power reserves more, perhaps exclusively, towards arcane casters.

There's also the potential, which I hadn't originally considered, to make using divine magic in opposite-aligned sanctified areas, or any magic in magic-suppressed areas, more expensive. Maybe it could be expressed mechanically by a simple numerical degree of resistance, being the extra hit-point cost one would have to pay to push through that resistance and get one's own magic to work.

 

[bedir than]

Can you use someone else's energy to cast spells?

 

[PeterFitz]

Can you use someone else's energy to cast spells?

It's not something I'd thought about, but I guess it could be considered an extension of necromantic magic. It would have to be the same sort of power level as other energy-draining spells, plus a bit to account for the fact that you get to make use of the energy being drained.

I see no reason why a magic power reserve couldn't be charged by one person and then used by another.

 

[steeldragons]

3 Cantrip castings per 1 HP
1st lvl spell = 2hp
2nd lvl spell = 4hp
3rd lvl spell = 7hp
4th lvl spell = 11hp
5th lvl spell = 16hp
6th lvl spell = 22hp
7th lvl spell = 29hp
8th lvl spell = 37hp
9th lvl spell = 46hp

Divine magics being cast in an area of opposing alignment, double hp cost.
Druid magic being cast in metropolitan/non-natural surroundings or areas of extreme (good or evil!) alignments, double hp cost.
Magic "dampening" areas or low magic settings, double the hp cost.

Magic of any kind being cast in anti-magic areas...seems self-evident. It doesn't work.

 

[bedir than]

It's not something I'd thought about, but I guess it could be considered an extension of necromantic magic. It would have to be the same sort of power level as other energy-draining spells, plus a bit to account for the fact that you get to make use of the energy being drained.

I see no reason why a magic power reserve couldn't be charged by one person and then used by another.

This makes the most powerful mages in your world very evil.

 

[GreenTengu]

You make a good point — I shall have to do some calculations.

Something else that was suggested is the advantage that high-hit-point casters (e.g. clerics) would have. That could be balanced, I think, by focusing the creation of magical power reserves more, perhaps exclusively, towards arcane casters.

There's also the potential, which I hadn't originally considered, to make using divine magic in opposite-aligned sanctified areas, or any magic in magic-suppressed areas, more expensive. Maybe it could be expressed mechanically by a simple numerical degree of resistance, being the extra hit-point cost one would have to pay to push through that resistance and get one's own magic to work.

Right, classes with higher hit point totals will be able to cast more under your system and it isn't simply Cleric vs. Wizard. In the PHB, casters are

Bard (Arcane) - D8 hit die
Cleric (Divine) - D8 hit die
Druid (Divine) - D8 hit die
Eldritch Knight (Arcane) - D10 hit die
Paladin (Divine) - D10 hit die
Ranger (Divine) - D10 hit die
Arcane Trickster (Arcane) - D6 hit die
Sorcerer (Arcane) - D6 hit die
Warlock (Arcane) - D8 hit die
Wizard (Arcane) - D6 hit die

It isn't a matter of simply Arcane vs. Divine exactly-- granted, there is no Divine class that has D6 hit die right now (unless you are using a UA variant of Sorcerer), but the issue we can see here is that this system would mean Eldritch Knights and Paladins would effectively become the best casters.

The best fix here is to not use a universal system. There needs to be a modifier depending on the hit die of the class and whether the class is meant to be a full caster, half caster or 1/4th caster.

 

[Connorsrpg]

I love the idea behind this. Will need a lot of tweeking to find exact amount and perhaps you will need to give casters more hit dice, or you have 2 pools with same effects if magic pool or hit points reach zero. I like the idea of magic draining you though. That is very much a part of the literature. Perhaps wizards just tire faster as their magic is more powerful.

But things coming from an overall pool sounds great. I have recently also been playing Cypher System and it tales some getting used to when resources are powered form the same source(s) as health. Takes time to learn the balance on what to spend and what to retain for defense - but that is part of the fun

 

[Rhineglade]

Not sure if this is a good idea. The theory is intriguing but I think it would lead to an unbalance. Too much tweeking could result in the wizard/spellcaster class being too powerful OR too weak. Wizards in particular have so few HP compared to other classes. Would they be so willing to ebb away their life to cast a spell? In dire straights maybe, but for something mundane?

I also keep having visions of the "Channel" card from Magic: The Gathering. Way too unbalanced.