Arkrim:
It would simply make spellcasting more ability-based and less automatic.
I suppose this wouldn't make sense if you are not familiar with d20 games.
Well, you have 6 primary attributes called "abilities" in d20 games: Strength, Constitution, Dexterity, Intelligence, Wisdom and Charisma.
These determine a bonus or penalty to a lot of rolls and actions you make.
In the game, spellcasters grow in power exponentially based on their level. Wizards use Intelligence to give them a few more spells and make their spells harder to resist, but the bulk of their power is purely level based with Intelligence just being the cherry on top of their sundae. Spell damage, range, area, duration, etc. are all based on their level and they increase really fast.
The problem with the way it's set up is that you can easily make a cleric or druid or whatever with only the BARE minimum spellcasting ability score needed to cast spells and then put all their other points into physical stats. Then cast spells that boost your physical attack and suddenly you're a more powerful fighter than the fighter, a better barbarian than the barbarian and a more skilled ranger than the ranger.
To avoid this from happening in the game, I chopped a spellcaster's benefits from level in half and increased their benefits from a high spellcasting ability, it wouldn't weaken them but would make them more dependent upon having a high spellcasting ability.
That way, a 10th level Wizard with 25 Intelligence is OBVIOUSLY superior to a 10th level Wizard with only 15 Intelligence, rather than them essentially being the same.
It also has the added benefit of helping to make them advance more linearly and less exponentially. They start off more powerful (just strong enough to put up a fight really) but don't become demigods of magic at higher levels unless they specialize in their spellcasting ability score.
This message was last edited by the GM at 18:09, Sun 27 Sept 2015.