Sorry you don't like a counter opinion. Let's be honest, whenever these restrictive mechanics are proposed they are always aimed at martials. When do see spell failure, or casting rolls or divine refusal aimed at casters?
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Ah verisimilitude, when you get tired beating martials with realism use verisimilitude as the excuse. Its funny how casters always avoid these beatings.
Are you a card carrying member of the Spellcasters Supremacy Society? There is already a wide enough gap between casters and martials without reducing their one glimmer of hope.
Looking at picking up a new system. I am currently leaning towards either Shadowdark or Dragonsbane. How to they compare and what are their selling points for those who have tried one or the other or both.
I would reboot prior to death of the Sorcerer King of Tyr, back when the shadow of the Sorcerer Kings covered all hope and there was no thought that they would or could be killed. Any hope in the setting had to be created and harbored by the PC's.
Reboot time, Sorcerer Kings in charge and trying to become Dragons. Dragon at large and nobody knows what its goals are. Preservers have to hide in the shadows. The world is dying and life is cheap.
If you look at the page for the revised 2e Darksun effects of Preserver and Defiling magic I pasted above you can see the choice was made when memorizing the spell.
So to be exact with defiling in the revised 2ED Dark Sun, when memorizing you make the choice to defile then make an Int check. On a failure lose effective spell level on spell. On a success cast as normal. On a success greater than amount based on local terrain, cast at higher spell level. Also...