To keep Nimue from causing damage, Merlin created the Dark One's Dagger via a tethering spell to control her; however, she stole it and used it to turn Merlin into a tree.
Merlin created the Dark One's Dagger via a tethering spell. This was to control her. This was to keep Nimue from causing damage. She stole it. This was however. She used it to turn Merlin into a tree. This was however.