watching scar and joel's episodes first and hearing impulse shouting that grian knew there was a cave system when he suggested the vertical mining thing and I was thinking "lol I'm sure grian figured that there was a cave system below but i don't think he knew for sure" and then i watch grian's episode where he stumbles upon the cavern and starts cheerfully explaining how he hopes the vertical mining will end up killing someone for demise and i just. i should not be surprised like yeah ok typical grian behavior.