One of my friends decided she was going to run a one shot adventure and asked our group to start pinballing character ideas. I find one shots to be the perfect arena for playing classes that I don't completely love and/or the more ludicrous character concepts. Per usual, I read all the class descriptions in the PHB for the 20th time, but I had an interesting idea this go round. CHA, WIS, and INT are the only abilities utilized for spellcasters.

And it makes sense. Those are the 3 that measure mental aptitude, as opposed to STR, DEX, and CON that measure physical. A Bard SHOULD use CHA, a wizard INT, and a druid WIS. However, is it inconceivable that, say, a sorcerer could use CON? It's an innate magic, so naturally no real INT nor WIS would be required to cast. That only leaves it's current ability in CHA. But, and maybe this is more RP centric, but I don't believe a more charismatic individual would necessarily make a more potent caster as a sorcerer.

As previously mentioned, a sorcerers magic is innate. So I could rationalize CON as a bridge between mental and physical aptitudes as you can be both mentally and physically tough, and they both usually (but not always) play off each other. It would take some serious fortitude, natural or learned, to control something so powerful that's coursing through your fabric incessantly. Concentration is also important to casters, which is tied directly to CON. So a caster less likely to lose concentration could be an invaluable asset, be it for attacks, buffs, or debuffs.

I understand that there are no skills that align with CON, thus leading to less cogent use of some, seeing as your normal ability would be lower to make points for your CON and none to regain those lost skill points. But it adds an interesting dynamic also where you could have a more tanky caster, not necessarily consigned to only ranged attacks. 

Any thoughts? Has anyone tried this at home? Or does anyone have data supporting why it's inutile and good as is?

Charisma isn't just personality. It refers to your presence and impression upon the world. It's the ability of somebody using what is inside them to manipulate the world around them. Basically, it's the Soul stat. This is also why effects regarding teleportation commonly require a Charisma save - not because the spell is doing anything to your personality but rather to uproot your presence in the world and putting it somewhere else.

Since most of the Sorcererous Origins have nothing to do with blood and all of them could be flavoured as something entirely unrelated to blood, Con is not thematically more appropriate. And no, Con is not a mental stat. You use it for a concentration check only because of taking damage: your ability to resist the pain enough to focus through it.

They tried letting a Sorc use Con instead of Cha for a UA subclass and it ended poorly by being very broken especially when multiclassing. As a result it never made it to be published officially.

CON as a spellcasting stat can get very unbalanced very quickly (see the Scarred Witch Doctor in Pathfinder, when they published it, it gave CON as the casting stat, and then they had to errata it so it stayed as INT)

Any specifics as to how it was so broken? Just curious.

There is precedent for "physical" stats being used for spellcasting. In the 4e Arcane Power supplement, the cosmic sorcerer used Strength for its main feature and many attack spells. The base infernal warlock in the 4e PHB used Constitution for most of its abilities as well. These lead to some weird builds, but it's not as unbalanced as one might think. For Strength, most casters are going to stay out of melee on account of their lack of armor proficiency and low HP. For Constitution, you'll have a caster with higher HP, but they'll be no better at weapon attacks nor using any skills. On the other hand, having Dexterity-based casting would probably be broken in most cases, as Dexterity is already the most useful stat for attacking with ranged weapons and finesse melee weapons, boosting AC, employing Stealth which is arguably the most useful skill in the game next to Perception, and for making Dex saves which are very common.

The main reason I see for the relative ease of balancing Intelligence-based casters is that Intelligence is the least generally useful stat in the game for anybody but a caster.

My thought process was along the lines of, okay with CON instead of CHA, there's more HP and a higher chance of not losing concentration. The trade off is some of your skills will have lower modifiers as (if using standard array) you'll put your highest in CON which has 0 skills attached to it. Seems like a fair, unbroken tradeoff to me. Hence why I asked for extra information I may not be privy to.

Normally a Sorc has to put points into CHa, Dex and Con but a combat focused Sorc with Con as the spellcasting ability can now focus on Con with Dex being secondary. The skills thing is not much of a tradeoff especially if you have another cha-caster like a Bard, or you have Charm/Dominate spells or Suggestion (Subtle Spell + Suggestion would get you through any social situation, no Cha needed). If you're in a dungeon-crawler / combat-heavy campaign then you can forgo social skills entirely anyway and can now treat Cha as a total dump stat.

Because Cha is now not a concern for you anymore, you can more easily become combat-maxed-out with less ASIs and therefore at lower levels.

Because your spellcasting is now Con, you are now a multclass dream since you can now multiclass with any non-Barbarian class with complete synergy. No longer do you need to be concerned about becoming too MAD! For example a Fighter-Sorcerer multiclass was tricky due to having to focus on both Str/Dex and Cha as important stats with Con secondary - leading to difficult choices on what to focus on. But, with Con as the spellcasting ability this is a thing of the past! Even if you want to primarily focus on sorcery, a 2-level dip of Fighter means you can just put Str to 13, get heavy armour (hello Plate and Shield) and never have to worry about any stat except Con. You can max-out your Char for combat so easily and quickly since you only have one stat to focus on instead of three. And it makes spell choices easier since you don't need Mage Armour and don't need to focus as much on protection - you're as protected in battle as any Fighter!. Sure you get less health, but it's not a huge difference when you still get to range-blast enemies and you can still chug a healing potion and blast a fireball thanks to Quicken Spell or Action Surge. Normally a Sorc doesn't have the Con to be OK with this even with the armours, ah but those armour profs AND getting to focus on the health stat AND still max your spellcasting? Yeah, that's broken. If you're using feats in your game (and who doesn'?) you can start with Mountain Dwarf for +2 Str and +2 Con and Medium Armour prof, which means one feat later at level 4 - roundabout the time you can afford half or full plate depending on your lootables, you can bump up to Heavy Armour prof and get +1 Str, so hitting that armour Str prerequisite is no problems. Then just a matter of Shield prof but with Shield spell and findable/buyable magic items, it's not a big deal to go without, but then another feat can get you it and since you only have 1 stat to focus on ASIs later, you have the freedom to get it. And this is all based on Point Buy, if you rolled high then even better!

So, being able to focus all your combat ability into one single stat is broken. Not terribly game-shattering, no, but definitely broken. Even the Dexy Rogue needs his Int and some Con. Being able to do everything a Sorc can do and only having to really focus on just Con is a bit much.

Completely understandable. I didn't put too much thought into the multiclassing aspects. Figured I'd let yall do that 😆. I wonder what the solution would be to fix it a bit. The idea seems cool enough, but maybe that's just me. Or maybe the viable solutions are just too cumbersome. Ah well, it was a decent thought. Maybe I'll have an epiphany one day about a solution.