Discharge of static electricity

I'm doing an EET playthrough with SCS installed, I was fighting some spiders in Cloakwood when this happened:

I didn't even know static electricity was a thing in the game and I can't understand where it came from. I am using IWD spells but I hadn't cast anything that I think might have caused it.
Where did that 68 damage come from?

I didn't even know static electricity was a thing in the game and I can't understand where it came from. I am using IWD spells but I hadn't cast anything that I think might have caused it.
Where did that 68 damage come from?
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I didn't even know it was possible. This is my first time playing SCS and I didn't know static charges were a thing. I'm using the SCS default script for her though so she may well have done it.
I did fight some druids earlier on and one of them cast Call Lightning which kept hitting Imoen again and again and again long after the fight was over but I am pretty sure I rested after that so I don't think it could have come from there.