Rule regarding conduct towards props and set pieces that make up an encounter. From the Accelerant core rules:
"When you come across props that represent certain environments, such as tarp walls representing solid walls, you must play as if that condition was real. You cannot move tarp walls, you cannot walk across black pits, and you cannot enter areas marked out of game."
This rule governs roleplay for situations that require the player to use their imagination due to real world / prop constraints. Example: obviously the game staff could not really pour lava over the floor, so if an area is stated by staff or NPCs to be made of lava, players should role play in a way that reflects that (avoiding stepping in it, suffering from the oppressive heat of it, etc).