Man, this is an embarrassing blow to the proud Keyneth. Not only did Kiritsugu drew blood from him twice, but he destroyed his Magic Circuit. Magic Circuits are passed down generation by generation, the older the Magi family, the stronger the Magic Circuit. But the stronger it is, the easier it is for Kiritsugu to destroy it, rendering it pretty much useless even after regeneration.
Mage Killer indeed.
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