ending?

OK, I am very bad at summarising stuff, and I am extremely biased in Mab's favour, so this is likely to be a strange summary, but here goes.

I'll go from just after Guinevere gets rescued by Lancelot, my apologies if you've seen most of this already, or haven't seen up to it but I'm a bad judge of time, so can't think what the last half an hour would be.

Basically, after Merlin causes it to rain, and Lancelot comes to rescue Guinevere, Mordred accuses Arthur of having Merlin save Guinevere after she had been found guilty of treason (which he did). Mordred says that this shows that despite Arthur's promises of a system of equality, the system of "one law for the rulers and one for the ruled" is still in practice. Having accused Arthur of hypocrisy, he tells him that he is going to destroy him. He leaves Camelot, taking several supporters with him.

Merlin comes across the Father Abbott from Avalon Abbey, who has ridden to Camelot to tell Merlin that Nimue has gone, and is waiting for him at the Door of Magic. Merlin accuses him of lying. The Father Abbot laughs somewhat evilly, and changes into Mab. She and Merlin exchange not-so-pleasantries for a while, and Mab reveals that Frik has left her employment (she doesn't tell Merlin the reason, but, as Merlin already knows that Morgan Le fay is dead, I'm sure he can guess). She also confirms that Nimue has gone, and that she is waiting for Merlin, then Mab vanishes.

Merlin goes to Arthur, who tells Merlin that his knights don't want Merlin with them in the battle against Mordred (ungrateful bunch of dunderheads that they are). Merlin agrees, and tells Arthur that he is going to find Nimue, and spend the rest of his life with her. They wish each other luck.

Merlin takes Sir Rupert, and they find the Door of Magic in a forest. they go in, to find that Mab has created a replica of Merlin's childhood home. Nimue is also there, free of scars.

Meanwhile, Mordred and Arthur are in the midst of battle. Many soldiers are fighting on both sides (including the turncoat, Frik, who is now fighting for Arthur). When Mordred and Arthur come face to face, they fight, and succeed in killing each other, much to the dismay of Mab and Merlin, respectively.

Merlin leaves Nimue to go to Arthur. However, unbeknownst to him, there is an enchantment on the cave, and when he leaves, the cave seals itself, trapping Nimue inside. Merlin is distraught and angry, but goes to Arthur anyway. Arthur gives Merlin Excalibur. Merlin throws it back to the Lady of the Lake, who reveals that Galahad, not lancelot, was the hero from Joyous Gard. She then vanishes, we presume that she fades away and disappears.

Mab goes to Mordred, but can't save him from dying, no matter what she does. When he dies, she is furious and upset, and seems slightly older and weaker- her hair gets white streaks in it, and her clothes are paler.

Merlin and Frik meet up with each other, and together they go to try and stop Mab. They find her in the empty city of camelot, sitting at the Round Table. She threatens Frik, who runs off, leaving Merlin and Mab to battle it out. Mab pummels Merlin for a little while (Not literally, obviously), but doesn't manage to do any real damage. She blasts a hole in the door, revealing a crowd of people standing in the hall. Assuming that Frik has summoned them to Merlin's aid, she isn't worried, until Merlin reveals that he has no intention of fighting her any more- he's going to forget her, instead. Everyone turns their backs on Mab, and walk away. Mab begs Frik and Merlin to turn around, but they ignore her, even when Mab tells Merlin that she loves him, as a son-its up to the individual viewer whether they believe her or not- personally, i do (And I scream at the TV "Listen to her, you idiot! turn around! Don't walk away" and other such things, including some unsuitable for posting here). With no one left to remember her, Mab fades away. (Then I throw things and get angry)

Old Merlin then finishes his story. One of the audience turns out to be Frik, who tells Merlin that Nimue is alive, and free from Mab's spell. Merlin goes to his old home in the woods to find her. With the very last of his magic he makes them both young again, and that is the end of both the film, and of magic.

There you go. Hope it helped