One of the few survivors of The Great Purge during the Clone Wars, Merrin guarded Dathomir with her undead Sisters and Brothers. A Jedi named Cal Kestis came and helped her destroy a Fallen Jedi Taron Malicos.
Merrin then joined Cal and his crew, and helped with her Night Sister powers.
Later after exploring the galaxy apart from Cal, she reunited and they confirmed their feelings with a kiss. She also was intrumental in helping keep Cal fron falling to the dark side, though she spoke a omen that love often ended in tragedy.