I should have told you that.  There was no electricity here with which to power anything, and their spells could not be made to work now.
I wish I'd told you that the lack of electricity won't allow their spells to work.
mnli hypothesis: I wish I'd told you that the lack of electricity won't allow their spells to work. premise: I should have told you that.  There was no electricity here with which to power anything, and their spells could not be made to work now.