User blog comment:Fimber/Things that went wrong in "The Death Song of Uther Pendragon"/@comment-7285162-20130415005522/@comment-5674726-20130603111152

''When Morgana was dying from her scull fracture, it wasn't just a scratch. When Arthur almost died two times and when Balinor and the sorcerer (forgot his name) healed him, it wasn't a scratch either. Both would have ultimately died if they hadn't been healed by magic. The life-for-a-life-policy was quite clear in "Le Morte d'Arthur". A life has to be taken in order to heal or create another. So I think that it was only done by Nimueh and/or the Questing Beast and it all vanished when both were dead.''

I think that you're giving the writers a bit too much credit.

I'd say that it's more likely that it was no longer convenient for them to acknowledge the established canon that the Law of Magic required that the Balance of Life and Death be maintained because they didn't want there to be a serious ethical barrier to the healing of any of the major characters by magical means, as it would mean that Merlin was sacrificing somebody's life if he healed Arthur of a mortal wound. Can't have the Designated Hero doing that sort of thing. I was horrified to see the Druids heal Sir Leon with the Cup of Life, given that they were supposed to be a peaceful people, and had just killed somebody.