Yesterday, I was a little bored, so I tried blowing up some guards with lightning runes for fun. After eagerly waiting for the explosion, nothing happened. This works perfectly fine with normal citizens, so I'm not quite understanding why it didn't work.

Rune spells don't affect people who are friendly to you, like followers.

It should work if you make the guards hostile first.

That didn't work either. I punched a guard and lured him over to a rune and nothing happened as well.