When I watched the first season, I thought the show was okay. I know the characters, but they are all mixed up. It is a good show as a fantasy using minor amounts of the Arthur mythos, yet didn't deliver for a first season.
Since the second season has started, at least it is following the mythos a bit more. For example, Arthur has shared his first kiss with Guinevere, his soon future Queen. And the additional content from one of his trusted Knights Of The Round, Sir Lancelot. And Mordred, another Knight, and traitor to King Arthur by fatally injuring him at the Battle of Camlann (killing himself in the process).
Also finally Lady Morgana as the evil sorceress, Morgan Le Fay (Arthur's half-sister). She is also known as the 'lady of the lake'. The one who gives Arthur the sword Excalibur. And yes, if you were wondering, Arthur did not pull this sword out of a stone or a grave. It was given to him when the sword which he pulled out of a stone to prove his worth broke in battle at the Battle at Mount Badon, the sword which was named 'Hippaforalkus'. When he pulled out this sword, he was deemed worthy to be King. And yet, he was never a prince.
I find it interesting that they set the story at Camelot. Knowing that many know that Camelot was a myth back then as well. The Knights of the Round Table was created in search of the legendary Camelot. No one knows if he had ever found it. King Arthur was known to find treasures and hide it at 'Avalon'. 'Avalon' is also known to be thought as the burial place of King Arthur. No one truly knows where 'Avalon' is, but recent discoveries have led mythologists to Glastonbury Torre. It is believed that Avalon lies underneath the Glastonbury Torre, yet they are not allowed to do any excavation in the area.
And Merlin, the very well known Archmage of the Round, Friend to King Arthur. He was never a servant to Arthur, but more of a councilor. Yet his many lifetimes of living would have set Merlin to be more than 150 years old when he first meets King Arthur. Merlin knew Arthur would be King at his birth. (Merlin is known to be the one who enchanted the mother of King Arthur)
He is known as Merlin Ambrosius. But earlier in his lifetimes, he was known as Myrddin Emrys (It was hinted in the show when Mordred called Merlin 'Emrys') If you follower to earlier writings of Merlin, he was also known as Moros Lal. Which would have made Merlin much older. But when following the Merlin myth, you'll come across more of the name of Myrddin.
I did enjoy the show as it was a fun way of recreating the myth, but hoping it doesn't leave the original Arthurian mythos. From knowing the myth, I could speculate of what might come.
* Introduction of Sir Kay (interesting for this story as Sir Kay is also known as Gaius or Caius) as one of the first to join the knights
* Gawain as Arthur's nephew.
* Creation of the Morrigan (Morgan le fay's Four created evil witches)
* Merlin as a skilled warrior. (interesting as the mythos shows that Merlin teaches Arthur how to fight)
* Arthur becomes King (interesting how they do it as Arthur was never a prince)
* A closer relationship with Arthur and Guinevere (interesting as she is a servant in the show. In the Mythos, she is the daughter of King Leodegrance, the king which donates the Round Table as a wedding gift.) And later the love affair with Sir Lancelot. (Their betrayal of Arthur leads to the downfall of the kingdom, and later she marries Mordred, fathering him sons)
* A rivalry between Merlin and Morgan Le Fay (Lady Morgana)
* Battle against Saxon invasions defending Camelot (In the mythos, defense of Britain as one of Britain's greatest Kings)
* Merlin tells Arthur about his abilities (In the mythos, there were no secrets between them and Arthur knew Merlin's past lifetimes.)