Specific fic merlin dies instead of guinevere

[a h]

Hi
So in the fic i am searching for arthur and gwen can't have a child so they make a deal with the old religion like it happened with Arthur's birth. However,when the child is being born merlin dies instead of gwen.
It was implied that it was because merlin was the one Arthur really loved. I think merlin sort of falls down in the armoury and is seen by leon.
If anyone remembers it please do tell.
Thanks