Speaking of seances this reminds me of when I was a teen and we use to play around with this, pretending to put people into “trances” and trying to summon spirits. Well one time in the basement of a friend we are doing this and their German Shephard starting whining and booked up the stairs. Friend’s mother then yells down asking what we are doing because the dog is calling something to her attention in the basement. Pretty weird.
Animal Planet ran a great series called “The Haunted”, which was about how animals are sensitive to ghosts/demons etc. Your “seance” probably conjured something up that scared the dog but that you didn’t notice.
Attempting to contact the dead is like opening up your front door and inviting anyone who passes by to come in. Even hard core “necromancers” say that ouija boards are dangerous. But like most things that are dangerous you are going to get away with it most of the time. But if you do end up inviting some creepy entity into your life it can be dang hard to get rid of it.