Constitution Based Caster?

[AgentPaper]

This is an idea I'm mostly just throwing out there, for anyone to use if they want. I don't know if stuff like this has been thought of before, but a precursory search brought up nothing. So, here we go:

My idea was something like a Channeler. Instead of casting spells like other casters, he merely has to "channel" magical energies of various types through himself to create a desired effect. The spells themselves would be the same as those on the sorcerer/wizard spell list, though you could easily make a divine variant, or druid even. However, a channeler doesn't prepare spells each day, and in fact doesn't even have a specified number of spells each day.

The basis of the channeler is that, when he casts a spell, he has to make a constitution check. This check would likely be something like: 10 + Spell Level + Exhaustion. Exhaustion would be a modifier that goes up the more spells you have cast that day. Casting any spell adds 2 to your Exhaustion for that encounter. After that encounter, that spell would only increase your exhaustion by 1, instead of 2. So if you cast 5 spells in a single battle, all of your DC checks to cast spells increase by 10. After that fight, though, in your next battle, your DCs would only be increased by 5. If you then cast 4 more spells in that fight, casting a fifth spell in that same fight would have a DC mod of +13. After THAT battle, the DC would go down to +10 for the rest of the day.

I believe that this system allows you to improve spell casting by, for one, not explicitly limiting spells you can cast per day, but also not making each spell cast trivial. If you cast a bunch of spells early in the day, it's not impossible for you to cast later on, (a natural 20 always succeeds) but it will be much riskier. For example, if you fail to cast a spell by more than 10 or so, it backfires, you take damage based on the spell level, and take "permanent" (has to be healed) constitution damage as well. A natural 1 automatically fails, though it doesn't automatically backfire. (if a natural 1 puts you 10 below the check, the spell backfires, of course)

This system is, of course, still very raw, but it's just a very basic idea for someone else to homebrew up a class from. I just like the idea of a con-based caster.

Edit: Not sure how this got here, instead of the homebrew section. If someone could move it there, that would be nice.

[thegurullamen]

I'd say it's a nice idea in theory but has too many similarities to the Truenamer "caster" class from the Tome of Magic. I was about to suggest something based off of the information you've given focusing around channeling magic through the body to augment it (uber self-buffer), but then remembered that obscure book "Magic of Incarnum". Con-based caster-types can be found in there, but not full on Sorc/Wiz/Wu-jen/Etc. types.

Keep toying with the idea and if anything comes of it, post it on the homebrews.

[Tempest Fennac]

There is a Shugenja variant which uses different stats for casting, and the Earth specialist uses Con. There's another class called the Tantarist which uses Con, but I don't know anything about them.

[SoD]

I don't recall ever reading or hearing about those variants...what book/mag/web site?

[ghost_warlock]

In old 3.0 psionics, each of the different disciplines was tied to a different ability score; Str was psychometabolism, Dex was psychoportation, Cha was telepathy, Wis was clairsentience, Int was metacreativity, and Con was psychokinesis. If you stay away from the psionic combat, you might find some good ideas in that book.

Also, the totemist in Magic of Incarnum is Con-based. Although not technically a caster, it has some interesting abilities and the soulmelds it can make grant some diverse and evokative effects. A very cool class, imo, that you many want to check out. I think it also uses a check of some sort to craft the soulmelds, but I can't recall for sure.

Another idea I had is based off a spell points system, like that in Unearthed Arcana, but somewhat different. It might be a bad idea in practice but I think it'd be an interesting mechanic to give the class d10/d12 Hit Dice (instead of the d4/d6 casters usually get), but make the class burn hit points to cast their spells. For example, if a 5th-level character would normally spend 5 spell points to cast fireball, this class would instead take 5 points of damage when casting the spell. Essentially, their spell points and health would be come from the same pool. When a character was down to their last few hp (maybe 1/4 of their normal max), you could make them fatigued to prevent them for casting themselves to death...or you might just let them go at it however they want and suffer the consequences for their recklessness (desperate times and all that). Feats like Toughness and Improved Toughness might very well become must-haves for a class like this. You could even give them an ability/feat like the psionic feat Body Fuel that allows them to take ability burn in exchange for more spell points (the psionic version inflicts 2 points of ability burn to Str, Dex, and Con in exchange for 2 power points, but characters can burn more at a proportional rate for more power points - 4 points from each for 4 power points, etc.). Mind Over Body would be another great feat to have for a character with this kind of an ability. Some of the other psionic feats that allow various augmenting of powers could be cool for a class like this, too - spend extra hp to apply metamagic and the like (up to a maximum of hp per spell equal to their caster level, of course). You could allow Overchannel, too, so that they can raise their CL for one casting by up to 3, but take even more damage when doing so (1d8 for +1 CL, 3d8 for +2 CL, 5d8 for +3 CL).

Anyway, just some ideas.