|Chainmail Spell Complexity from here
A while back, Jeff wrote a post about Chainmail-style roll-to-cast magic. This came to my attention again recently because Jeremy was discussing using a similar system to replace spell preparation. And then I saw this by Brock about replacing cleric spells with general “miracles” and a saving throw mechanic. The details of that system are not important for my purposes here, save one: every miracle granted imposes a -1 cumulative penalty on future attempts.
What if we combined Chainmail casting with a cumulative penalty? A point of “arcane stress” would accrue to the magic-user upon any result of delay or worse. At no point is a magic-user ever prevented from attempting to cast, but the more they cast, the less reliable magic becomes, and the more likely a mishap or backfire will be triggered. This could entirely replace prepared spells, yet maintain a cost to casting.
Like my save to retain spells variation, it makes lower level spells closer to at-will magic as magic-user level rises without actually removing resource management (the resource cost comes in the form of potentially making future spell casting more difficult). Arcane stress goes away between sessions or adventures (basically, any time that a character would traditionally be able to prepare spells). It has most of the benefits of a spell point system but far superior atmosphere (in my opinion, at least).