[quote=@Silver Carrot]
Hmmm, what kind of ancient spirit would grant the user lightning powers?
[/quote]
A Japanese spirit (a shrine priestess to Susanoo, or maybe even a kami); a sailor and/or pirate; or Nikola Tesla's assistant who was caught in a lab accident and received electricity-based superpowers.

Also, as an alternate approach to RBY's:  someone who maintains her calm, her dignity, her gravitas, until enough tension has built up and she snaps with all the rage of a billion volts.

[@RBYDark] Her [i]bear hands[/i] indeed. :lol
Nice notice that Agmundr is probably old enough to have gone through this before!  Kammu, not so much.