Hi,
I'm on the prison to free the witch and I can't pass the sentinels, even when they're turned on their sides they spawn the lava, I tried invisibility spell and teleporting people to the middle of the room and they still spawn the lava. I seriously think this is bugged.
Yeah, they shouldn't be able to detect invisible chars. Try to give one person 100% fire resistancy (potions, gear) and run through. In the next room there is a chain to deactivate the sentinels for the rest of the party to proceed.