Board Thread:General Discussion/@comment-28319791-20160507034922/@comment-5674726-20160507141200

I have a theory about Morgana's invulnerability to mortal blades, namely that her healing bracelet worked by attracting healing magic if the wearer was injured and then storing that magic for future use.

Morgause used magic to block Morgana's nightmares, the bracelet stored the magic even after Morgause died. She was also drawn to Morgana when she was poisoned.

When Morgana was dying of a head injury, Merlin felt driven to use magic to save her, despite knowing that she was an enemy of Camelot. He believed that it was because he couldn't bear the sight of everybody else's grief but what if the bracelet was influencing him to make him want to use magic to save her? Since then, Morgana has had multiple head injuries, at least some of which could have been fatal - she may hold the series record for being knocked unconscious - but has always recovered very rapidly.

At the end of Season Four, Morgana was dying of a wound inflicted by a mortal blade. Is it a coincidence that Aithusa happened to be drawn to her and ended up using magic to save Morgana's life, or was it the work of the healing bracelet? It was only after Aithusa healed Morgana that she could no longer be killed by a mortal blade, hence my theory that Aithusa's healing magic was stored in the bracelet and was activated every time Morgana suffered a wound from a mortal blade.

As for Merlin, it is unclear what the deal is with his immortality. It seems that he won't die of old age but it's impossible to tell whether he is eternally young or if his old man form at the end of the series finale is his real body, not a disguise. I'd lean towards it being his real form. It is also impossible to tell if he is also invulnerable or if he can be killed.