Skill 50% 100%
Magery 20 40
Necro 20 40
Chivalry 25 50
Bushido 12.5 37.5
Ninja 12.5 37.5
Weaving 12.5 37.5
This little chart means to cast a magery spell 50% of the time, you need to be 20 points above the minimum skill requirement. To cast a spell 100% of the time, you need to be 40 points above the minimum. If it doesn't make sense, let me know and I'll try to explain further.