It refers to the fact that he has blick lighting running through his fur. Functionaly this is no different from his inherent ability to emit black lightning from his arms when he is in normal form.
Ultimately the lighting explains his +5 strength, making his attacks deal +5 more damage than he normally would... get it?
If he wanted to weaponize the lightning further than that then he'd need to rank up the spell again.
anyway this modification has been approved and therefore this thread is closed.