Darklion said:
This is a terrible mechanic, because it penalizes the wizard at the one thing he is capable of doing: casting spells. Since many spells are subject to saving throws to reduce or negate spell effects (quite a few spells are all-or-nothing depending on the saving throw result), some spells require attack rolls, and virtually all spells are subject to spell resistance, the ability of spells to actually affect an opponent is already fairly dicey. Requiring wizards to make a Spellcraft check PLUS saving throw PLUS spell resistance, PLUS a potential Concentration check should they try casting in combat or suboptimal conditions, PLUS the chance of failing an attack roll?
This would be like forcing a fighter to make a skill check to see if he can correctly swing his sword, before he is even allowed to make an attack roll against his opponent.
It gets even worse if a failed check for the proposed spellcasting check means the wizard loses the spell slot. Then the wizard chews up a very valuable resource -- spells per day -- simply trying to perform the most basic function of his class, and again, that's before he even has to worry about the spell failing due to a missed attack roll, spell resistance, or saving throws.
I like the basic idea of a casting roll, but you bring up some valid points. Currently D&D magic is based upon a relatively complex system of checks and balances that altogether make it difficult to add yet another random element to the Vancian system. I think that in order to make this work, you have to get rid of all the other extraneous details that inhibit spellcasting. The check result should determine how well a spell is pulled off (IOW, if the spell has the intended effect upon the intended target). There should be a base casting DC for the spell based upon the spell's level. The check result (if successful) determines the DC of any saves related to the spell, so it's naturally harder to save against well-cast spells, just as it's harder to Listen or Spot someone who got really high Hide and Move Silently results. SR should work more like a magical AC or DR. It could make someone really hard to "hit" with a spell or soften the effects of a successful spell.
The problem with using casting checks for spells is that unless you start with a ridiculously high DC for 0th level spells, chances are that a spellcaster of sufficient level has a bonus that exceeds the DC of the spell, and the only thing you'd roll for is to see if the caster gets a natural 1. I can envision a few ways that you can put a break on this. The basic assumption I am working with here is that magic should not be easy, quick, or simple, even for the extremely talented (18+ in the casting stat). Here are some ideas I have for that:
1.
Base the preparation time on spell level. This one applies more to clerics and wizards than the other classes. I envision prepared spellcasting being much like cooking. The most important ingredient is time. You cannot shortcut or bypass it. If you could, you probably have better things to do than play with pathetic little 9th-level spells. The rule I'd use is that spells have a prep time equal to one hour times the spell level. So, prepping a 9th-level spell requires 9 hours of preparation. This limits the total amount of spell levels to be used in a day to 16 (24 minus the 8 hours' rest required). If a caster wishes to pull an all-nighter and get those extra 8 spells, I'd probably impose a penalty to casting checks for the spells prepared equal to the hours of rest lost.
2.
Base the casting time upon spell level. This one applies to all spellcasters. A rule of thumb is to have a spell's casting time be equal to a number of rounds equal to its level. During combat (which is when most spells see a lot of action, hence the measurement of casting time in rounds), it isn't always feasible to take the standard time to cast a much-needed spell. Thus, you can try to rush through things a bit but at a cost. This is especially true for prepared casters, whose spells I imagine to be more ritualistic in nature. Even spontaneous casters need to pace themselves to trying to manipulate too much magic too soon. For each time you halve the casting time of a spell (minimum time 1 standard action), you could give a -5 penalty to casting checks.
3.
Determine the cost of failure...and success. As I stated earlier, magic should almost always do something, though whether as intended or not depends on how well you cast a spell. If a spellcaster fails a roll, he should count his lucky stars if nothing happens. Even a successful casting of a spell can induce some backlash, especially if a caster is trying to cast a very powerful spell (highest level available to the caster, above 0th), a lot of spells in a short amount of time, or if the caster is rushing things (see above). Backlash can take the form of temporary ability damage (especially Strength and/or Constitution; possibly permanent for catastrophic failures), nonlethal damage (becomes lethal after dropping below 0 nonlethal points), and other interesting side effects. If you can, take a look at the Paradox rules for Mage: The Ascension.
but Dark Legacies does have a system for corruption (taint) as a consequence of using magic. Taint could probably be integrated into a non-Dark Legacies magic system fairly easily, as it is based on the simple combination of the caster's Wisdom score and the number of times he learns or casts a spell.
