Is the drain save a will save or con save?
Actually, I think it would be made using the caster's Magic Stat... Since, afterall, this is supposedly damage is supposedly caused by the stress of handling magical energy..
With the existing snag rules, a horribly failed cast (fail by 10 or more) will give the caster snag points; a follow on save vs drain failure will additionally penalize the caster. Something to keep in mind.
Can you remind me where it says Saves are subject to Snags/Boons? I cannot seem to remember or find it in the book...
And note: that the failures of the save are intended to hurt and be cumulative. The idea is that eventually the caster will need to stop casting and recover....
This adds another roll. Maybe it's not an issue for most, but there's already many places where multiple rolls are needed in spellcasting (target saves etc). I like the Versus mechanic where one roll is used. I'd suggest using the same dice roll used to cast (vs CTN) as the number used for the drain save.
Interesting idea -- let's take a look to see what sort of results this might come up with....
We will use Cedric's stats (from the pre-gens in the Downloads area)
His total bonus for Spellcasting is 8. His Save Bonus for Wisdom is 8.
Divine Bolt -- his base CTN is 21 (SP2), so his Save vs. Drain would be 16. This means that if he successfully cast the spell (rolled 13 or higher), he would ALWAYS make the Save, essentially only taking damage if he failed in the casting, and even then, he would have to fail the Casting roll by at least 3 (i.e. roll 10 or less) before it would deal him damage. And since 10 or less is lower than the average die roll, chances are low that he would fail and suffer Drain.
The same sort of situation would apply to every spell that he cast. This could work as an option, but it would be a very powerful option since a successful is likely to always (I think) mean that the Save vs Drain is successful...
Now, if we were to use the same roll, I would say that the Save vs Drain would have to have a TN of (CTN + SP), so that for our Divine Bolt, the CTN is 21, and the TN for the Save vs Drain would be 23. Thus, if Cedric rolls a 13 (total of 21) he would take 2 hits of damage. If he rolled a 15 (total of 23, then he would take no damage).
And if he scaled up the spell (one casting option has a CTN mod of +4 and an SP mod of +2, that would make the CTN be 25, and Drain TN be 29 total... In the long run, this means that a caster would be MORE likely to take Drain when using Casting Options to scale up the power of a spell... but that is something I can easily live with....
As implemented the penalty is damage or a negative modifier though a condition like stunned or dazed.
Actually, it implements hits, AND either Dazed or Stunned, if enough hits are dealt...
However, this also offers a good way of introducing some variety into magic. For example, many games offer an idea - magic is dangerous and can corrupt. So instead of damage or stuns etc..the penalty effect could be some form of corruption such as a disease, mutation, etc..either a temporary condition if a moderate failure (miss by 10) or a longer duration (miss by 20). Or a drain failure table could be created for each type of caster (warlock, wizard, etc) with penalties that are appropriate or evocative of their nature.
Hmm... with Snag Points, then instead of Dazed or Stun, have Corruption tables that could be rolled upon randomly -- or wait.....
1 Snag Point -- have Drain Snag Table -- 1 Snag Point can get either Dazed or random roll on slight corruption table. 2 Snag Points can get Dazed 2 rounds, Stunned 1 round, random roll on major corruption, 2 Snag Points allow for 2 rounds of Stun or choice of one slight corruption, etc..