Well, Arthur could feel betrayed at first. He has been brought up to believe that magic is bad, and here his closest friend has been hiding this big secret. However, as he realizes how Merlin has saved his life and the kingdom many times with his magic, he might come to accept it and even see the potential of magic being used for the good of Camelot. For example, Merlin's magic has defeated many enemies secretly, which Arthur might now understand as a necessary protection for the kingdom.
Bandon Hill in the King Arthur story doesn't have a super - precise location. But it's generally associated with the areas in England that were important during the time the Arthurian legends were taking shape. These areas were often hilly and had strategic importance, so Bandon Hill was probably in a location that could have been a site for battles or a place where Arthur and his knights might have journeyed through.
The 'Arthur the King' trailer may draw on the true story in terms of the power struggle. In history, there were likely battles for control of the land. Arthur in the legend is often seen as a unifying figure. So, the trailer could show scenes related to this, like Arthur gathering his knights or leading his people into battle. Another aspect could be the social structure of the time. The Arthurian legend often features a hierarchical society, and the trailer might depict elements of this that were based on historical facts.
One consequence could be that Arthur becomes more aware of the threats around him. He might start to trust Merlin even more, seeing him as someone who truly has his best interests at heart. This could lead to Arthur relying on Merlin more in future situations.
From the story, you can learn about leadership. Arthur's way of guiding his knights and making decisions offers valuable lessons. Also, it teaches the importance of loyalty among friends and comrades.