Kill them all!
Henzell says...
  1. Spell success rates are coloured according to miscast severity. Grey means less than 0.1% chance of a severity 2+ miscast, yellow means < 0.5%, light red < 2.5%, dark red >= 2.5%.
  2. Note that Intelligence stat affects spell success 1/6 as much as average spell skill, and Spellcasting skill affects spell success 1/4 as much as average spell skill.

Information based on master branch and the great LearnDB.
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