as for his approach! merlin's going to be highly respectful (proper titles and everything, he remembers how to not get executed by royalty) and phrase the investigation as something they were tasked to do in his absence, but they knew that their results would be nothing if they could not ask the king himself their meaning. the curiosity of a fellow mage who's been practicing, but the respect from someone lower in status than him.

as for the answers! because we accidentally made team rune full of morally dubious jerks, merlin will respond that he doesn't know where the temple is, be somewhat vague on what it is (half because he doesn't know that answer and half because don't hand all your info to the enemy) and question why he wants to access it - whether it's because he wants to find another world to send his people to in case the coup fails or if there's a deeper reason.

(does he have to make a charisma check here or something)