Talk:The Disir (episode)/@comment-150.254.73.222-20130518111224/@comment-5674726-20130519000731

My theory is that Mordred's life was never in danger, the only question was whether the life of a friend or the life of a future enemy would be restored.

Had the Disir killed Mordred after Arthur agreed to their terms, he would have seen that as a betrayal on their part and turned even further against magic, breaking his vow to accept the Old Religion. However, had he accepted magic and the Old Religion, Kara, and others like her, wouldn't have seen him as their enemy, Kara wouldn't have tried to kill him, and wouldn't have been executed for it, which would mean that Mordred wouldn't have turned on Arthur. As High Priestess of the Triple Goddess, Morgana is likely to have been required to abide by the judgement of the Disir, and would have been ordered to lay off Arthur if he accepted the Old Religion.

Merlin may well have sealed Arthur's fate by choosing to protect him at the expense of countless magic users.