Each new loop began with her, and ended with her.
And each loop went the same way.
Arthur would be corrupted, Merlina would turn against them, a new king would redeem her once they smote Arthur down...
...and years later, she would turn against them again, causing the fall of Camelot.
This was a fact Caliburn knew well.
The knights were aware of the loops, as well.
Everyone in Camelot was.
The loop always starts anew.
All because Merlina was redeemed.
She didn't deserve to be redeemed.
And one brave hedgehog was going to end it all.
So, as he stood to face the monstrosity that was once the knights' ally, both him and the sword's souls as one, Caliburn told him to strike her down.
The hero protested, telling his sword that he always gave people a second chance more often than not.
Caliburn had no other choice left.
He told the hero everything.
About the inevitable fall of Camelot if he made Merlina see the error of her ways, the time loops, everything.
He wanted him to break the cycle, to end the time loops once and for all...
To kill her.
Again, the hero protested, saying that even if he had the choice between that and finding a more peaceful solution, he'd choose the latter.
And again, Caliburn asserted that killing her was the only option, that if she continued to live, he, along with the people of Camelot, would be forced to start over, over and over and over again, with no end.
The hero protested one last time, only to be interrupted with one last, urgent command from the sword to kill the enemy before them.
With reluctance in his heart, the hero slashed...
...landing the fatal blow.
It had been a few days since then.
Merlina was dead.
But life could finally go on without the fear of her repeating her misdeeds.
Without the fear that she would eventually betray them again.
Without the fear...of her.
Caliburn was back in Nimue's care, able to rest easy knowing that, even when Camelot faded into legend, that the hero, back in his own time and place, did the right thing.