Finished watching "King Arthur: His Life and Legends", the second episode of _King Arthur and Medieval Britain_ from the History DVD set. This episode dwells in greater detail on Merlin, Morgan la Faye, Mordred, Lancelot, and Galahad. Apparently there was one seat at the Round Table which only the purest knight could claim, and that knight was Galahad, who was the only knight successful in the quest for the Holy Grail.

The episode clarifies that Arthur had two swords: the sword in the stone and Excalibur, given to him by the Lady of the Lake.

More bits of information I never knew before:

--The power of Excalibur was not in the sword but in the scabbard
--Merlin's powers were vast but unspecified.
--Galahad's sword was one that had broken into three pieces and that became whole again once he claimed it.
--The Holy Grail is described in different texts first as a stone, and then as a platter, and then also as a chalice.
--The lake round the Isle of Avalon was known to separate life from death.