Spheres of power adding a new ability score

[Saffron-sama]

I have been think for a while about adding a new ability score for a spheres of power game. The ability score would be Arcana it would be the casting modifier for all classes and be the ability score for the Spellcraft skill.
What could be the consequences or what else could I use this ability score for?

[inuyasha]

Well, it could throw off the balance of point buy, and give an additional stat for mundane's to dump in addition to the usual Intelligence and/or Charisma.

If you roll, that's not much of a problem though.

You'd also have to determine if spells, magic items, and similar things can add to the Arcana stat, thus using magic to boost your own magical ability, and whether or not this costs more or less in item form than other ability scores, because it's a very specific benefit that's powerful to a specific set of classes, but useless for others.

[ComaVision]

Can you explain what the purpose would be?

[Fouredged Sword]

I somewhat like the idea, but I would always tend towards duel stat casting with spells per day based on one stat and save DC's and max spell level you can cast determined by arcana except for spontaneous casters.

As a game design I would have tier 1 be always duel stat, tier 2 require only arcana, and tier 3-5 mostly able to ignore arcana and put points into other stats. (for example I would give a bard a class feature at level 6 or so that allowed them to add their charisma to the save DC's of illusion or enchantment spells they cast to make it easier for them to not have high arcana)

[Saffron-sama]

Can you explain what the purpose would be?

To seperate the Caster from being a Genius, Wise or Charismatic making it more of a magic is its own thing and no matter how much you study if you have no talent in magic then you have no talent in magic.
It also allows me to make races good at magic (+2 arcana) without filling the race with a bunch of useless racial traits that take the place of more fun or thematic abilities.

For those who don't know spheres of power removes spells and spells per day in a different magic system which is why I mentioned it in the title.

I planned on using a modified version of Automatic Bonus Progressing which would include Arcana so I won't have to worry about magic items that effwct Arcana.

[DMVerdandi]

Came to a similar conclusion, and suggested it in multiple threads here (always end up calling mine Spirit, or Mana or some other supernatural nomen)

Here is my input on it though.

You should also have skills that are modified by the arcana stat. I know next to nothing about spheres of power, but I think in any game, having a magic stat is good. It like you said, takes the focus so much off of said stat. It also makes way for balanced MAD.

I think the coolest thing you can do is

1. Have SR as a skill.
2. Have vigor as a skill, where you can increase physical ability checks/skills, but with a burn afterwards
3.Detect Magic as a skill

And then have them for purchase as a feat. In this way, you can have even non-spellcasters benefit from the existence of the score.