How to build a semi competent mage

[Whitewings]

The concept is simple: high IQ, high Magery, lousy at casting. Her magic either blows up in her face (harmlessly), works, but not as intended, or, very rarely actually works as intended. I’m assuming effect shaping ritual magic, but I’m not sure how best to represent the “not as intended”’part. The “blows up in her face” part is easy, just use the comedy critical failure table.