Any time I spend outdoors is always helpful towards whatever project I am working on. To whit, I just took my dogs for a 20-minute walk, and returned having re-thought the spell system from the ground up.
At present, a standard spell casting attempt is a D12 +level check (DT 10). If you roll 9 or lower (altogether), you fail. If you roll very low (1 for rank 1-3 spells, 2 for rank 4-6 spells) you lose 1 mana point. However, as I pointed out last entry, I've created a special rule for buffs and healing spells that they only fail on a natural 1.
However, what if I made that failure check the standard check for all spells? Right now, the odds of spell failure are pretty high - as a level 3 caster (what I would consider having moved to the 'heroic' tier of the game), you fail on a spell 50% of the time. Now, odds are very good that by then you have some means of receiving +1 edge to the roll (increasing your odds considerably), and also that you are getting some bonus to checks (probably from a tag)... so that 50% in actual play is probably closer to 30%.
If we go with a system where you 'attempt to cast', this would be successful as long as you roll above the spell rank... so my level 3 caster has a 92% chance of casting a rank 1 spell (as all casters do), an 83% chance of casting a rank 2 spell, and 75% chance of casting a rank 3 spell. These odds are the same for a level 4, 5, or 6 caster, and are the same whether you have mind 3, 4, 5 or 6.
So a level 3 caster with mind 3 has a 75% chance to cast dispel magic... but so does a level 6 caster with mind 6. Meh. I mean, it's okay...
I like fair, but I love simple. So, here's a go at a simple system for this:
- Your mind sets the highest rank for spells you can cast.
- A spell is miscast (fails and costs 1 mana) if you roll half the spell rank or lower. So costs by rank are as follows: Rank 1 or 2 spells (roll of 1; 92% chance of success), Rank 3-4 spells (roll of 1-2; 83% chance of success), Rank 5-6 spells (roll of 1-3; 75% chance of success.). All casters have the same odds.
- A miscast spell cannot be attempted again for 1 minute.
- You can only cast cantrips if you run out of mana.
The reality is that many spells allow a resist anyway... so this is, in effect, using the old school D+D chance of spell failure system. Your level and mind are the things that grant you access to higher level spells, so the fact that they don't also mitigate spell failure is offset a little bit. Since casters will be going through more mana, maybe their mana is set at level + mind. Now, a smarter, higher-level caster has the same odds of failure, but has more chances to cast other spells to make up for it. Mana recovery would have to be pretty slow then... I think this just might work. Time to do some editing... and some play testing (which is great, because I'm about to take on another caster).
By the way, the odds with +1 edge (casting a signature spell with the tag or casting a spell while using a wand) reduce the odds of failure to 0.7% with rank 1-2 spells, 2.7% with rank 3-4 spells, and 6.25% with rank 5-6 spells. Most high-level casters are going to have these options, so they are going to be successful the vast majority of the time.
Hmmm. Now, I'm back to thinking of going with rolling the spell level or lower results in a failure and 1 mana. A level 5 or 6 caster casting a level 5 or 6 spell is very likely to have +1 edge to the casting check.